Lulu,
I had a 6cm right tonsil tumor - no pain and no bleeding. More often then not OC is asymptomatic so I would look at that (pain) as a good sign.

Acid reflux or GERD as it is called here is not something to fool around with - it can certainly lead to cancer eventually.
It is highly treatable. Modifications to diet, antacids, prescriptions, etc.

MRI's reveal very detailed images of soft tissue. They typically scan from the top of the lungs to the lower part of the brain for a head and neck scan. Obviously something is causing your symptoms but there are other causes besides cancer, such as peritonsilar abcess (PTA). You are wise to rule it out while it is so small. (Modern imaging usually can't detect tumors smaller than 2mm). By the way, all tumors in the US are expressed in the metric system.

Welcome to OCF and I hope for a successful outcome.