@ Christine 1st: thanks for getting back to me so many times, no need to apologize: the web is such a great resource, but sometimes takes a bit longer to explain, plus I do have the language issue that does not help.
Pls note my fault again, as I was not clear about my PET: I said I had a false POSITIVE 1st, then I clarified. I had such a bad Freudian slip and feel so scared, that I meant false NEGATIVE: sorry and forgive me if this generated a conversation on your false positives and so on.
I am getting the MRI results in a few hours, so hopefully no more sweat at least about worring for the PET-TC resulting into possible false negs (I read your DR and member's post few minutes ago, I cannot recall his name, and he says it fails detecting masses which are smaller than 2 CM).
In any cases I am so unsure about what is going on -until tomorrow morning, which is in 3 hours here.

@ Don, thanks for jumping into the conversation and yes, I am in EU, and there are major cancer centers here, namely the state-run Istituto dei Tumori and Professor Umberto Veronesi's IEO, both in Milan. Went to the 2 of them, and here is my own experience (posting in case this helps anyone):
IEO: I went first to see a Lung Specialist (at that time, we were still on the wrong side because of the coughing). Proactive attitude. Called me back in a week with a huge program of several tests, multiple rays and endoscopies. Program included the clearly stated possibility of 'lung surgery'. Unfortunately, as I can just tell this now, my General Doctor said it was exagerated. At that time, the fatigue was not still there and I was not aware it all came from the mouth so having already tested lungs, I somehow - do not why - listened to the GD. I was not persuaded things could worsen. Time dedicatd to me: 4 minutes, but a promise to give me an explanation. Cost for this consultation: 140 Euro.
Istituto dei Tumori (pls note this place has a great heritage and is so respected and well-reputated): I went months later, when I realized blood was from my mouth (despite other 3 specialistic consultation on the area saying it was just inflammed) to see an Ear & Mouth specialist; he did not even palpate mouth, said it is normal to have one-side pain for months, mentioned reflux despite me saying my EGDS was negative and referred to a little vein in my mouth (located far from where bleeding originates). Time dedicatd to me: 4 minutes, without adding anything new to my papers nor proposing any further tests to give me an explanatin (and a cure of course). Cost for this consultation: 120 Euro.
On a more positive, yet not helping end, I also met a Blood expert later on there (as the General Doctor who says I am healthy, sent me to the onco-aematologist for a 1CM lymphnode on my right neck: funny isn't it?). This person noticed my general status (incuding the look of my exausted face, my skin, my weight and so on), dedicated to me 1HR and 30 minutes of her time and suspected an auto-immune disorder. Way far from the solution, since she trusts her fellow on the mouth state, but still she was human and at least noticed a disease. The dept even called me back days later to see if I could find a solution.
You'll be able to judge the 2 (let's say 3) different approaches. The former looked very positively American to me. I was even offered a medical staff consultation, but again my family members, boyfriend and doctor were against this, and I failed listening to them and saying no IEO, the only place where I was offered a chance sofar.
The health system here is suffering as it is slowly turning from public into private, so there is a big confusion and it is also said that legal medicine is creating more and more issues with diagnosis. I am the living proof of this mess.
As in the US, if I am getting this right, we have General Doctors, but they are often unable to listen for time reasons and for knowledge lacks.
Then we have specialists, but they do not consult with each others, they do not hospitalize you for check-ups (well, they do not in general until you are almost dead), and they tend to avoid any possible jump into others' disciplines.

@ GPK101: thanks for your warm words, it does help to have virtual companions in harsh times and that is very delicate too. It does makes your day to read other people who do not judge symptoms as 'subjective', non-specific, non-measurable (that is what doctors say to me when I ask why I feel weak and lost appetite), or even worse, stress-related. They do not care when I say I feel the same despite a lot of rest and despite having had to stop my activities. Funny enough, the only person who is persuaded that sth is going on and this is not stress related, well, it's my therapist!
Family & friends, on their end, just keep on saying my tests are negative, then why should I care for some blood? It mustn't be scary. They say I cannot be tired after seeing all those negative results, that I do not want to trust the fact that I am healthy, then it's just about my mind, that's a matter of lost dignity, good-will and that it is not so difficut to eat properly and to be active; just note I have always been a even too hard worker, a very engaged person and a happy girl. They just keep on saying, relax and focus on your job (which I am about to loose). They seem not to see I look pale, exhausted, loosing my hair that had first become thin and opaque, fighting for every bite of food. Mostly they all say my worries are exahegerated and that none has proved I have a disease.
Appetite-wise, I am petite by nature so it was quite tough, now there's so many things, namely proteins tasting bad and this makes me feel guilty, and fatigue-wise, I had to stay home 24/hrs a day since a few weeks.
I even look younger than my actual age, so my doctor in General Medicine who seems to have prblms in dealing with young patients being involved with a major issue, kept on saying to me: get a holyday and you'll feel better. That was so frustrating (I had holydays, my last one was last summer, to prove my family I was fighting at any level, and felt so bad as I lost many energies during that time; I left for 2 days at Xmas, and this was pure torture as I could not be the actve person I was once). I forced myself to regain weight, which is why none would ever had run massive tests, namely hospitalization on me when the symptoms were not that clear despite the loss of weight and very scarce and isolated bleeding.
I was even treated with ant-depressant drugs, with no effect (except more bleeding) and my therapist said this was not the solution.

You'll forgive my I, I, I soliloque: that's my night (well, morning in a few hrs here), I am spending it on my laptop trying to connect with you all, trying to feel we are not alone, and that united we stand and we can fight.

It is pure relief to read your stories, to see how very human you are, all of you with a huge strenght, with the ups (many) and downs (so little), no matter the limitations. Everything seems possible tonight and I like to feel there is a family, and that one day even the weakest can be strong again and help back.

Sorry if I am quite pigheaded, and for the poem. I am without rest since a couple of months, which is why you can see me here at 5AM in a Friday night.

May you all have a lovely week-end with friend and family and with the things you love most.