Hi there - wow - I have to say I've been there - I know the feeling. try not to freak just yet! It it is an HPV cancer it does respond better to chemo and radiation, the PET should help locate the primary - there are different treatments depending on whether it is HPV related - if it's not usually - depending on location of the primary - first treatment is surgery... And since you've already had a lymph node involved likely they will do a neck dissection, and removal of the primary tumor - then possibly radiation and chemo. HPV + isn't always treated with surgery usually it's just radiation and chemo.

Re working - it really depends on the person - however - radiation and chemo can be brutal. Nausea is par for the course - radiation after week 4 - is very very very uncomfortable - and fatigue is also very common - I was supremely lucky as I didn't suffer too badly until week six - however I think I'm a bit unusual. I wouldn't count on working the whole time or your usual hours. Plus you may not want to be in public during the later part of treatment - often, depending on your skin type - fair skin has a more difficult time - you blister, and peel, and have excessive mucous In our mouth and throat - there's a lot of drooling and mouth - throat sores - etc. sorry to paint a bleak picture but I prefer to know the details up front, and sometimes it helps prepare for what's to come.

I'm sorry youre going through this - and sorry you have to be here!!! It was almost a year ago I received the same diagnosis - mine was not HPV related. I had surgery (there was a 2.4 cm tumor in my tongue - they removed that and part of my tongue and rebuilt it and took out 40 lymph nodes - one was positive) and 33 rounds of radiation and chemo x2. I am 46 - and not only someone who worked out daily - but was (still am) a vegetarian - who doesn't drink or smoke... And never have.
With regards to the feeding tube, I was told I had to get one. It was no use to me as I was allergic to the formula - and kept throwing it up - so I sucked up the pain and learned how to chug an ensure in 13 gulps!!! I did keep it in throughout treatment - its nothing really and heals quickly once removed. I lost 20 lbs - and another 10 after treatment because of the changes in my diet - radiation murders your tastebuds ( particularly if it's aimed at your mouth. ) So food becomes very unappealing.
As Christine said try to gain weight now. Good luck. And again sorry you've had to join our little group, feel free to pm mee if you have any other question or just need a shoulder - take care!