I sympathise so much with your worries.  I have just been through an absolute nightmare, the worst two months of my life, after a swollen tonsil was discovered on an MRI for a different problem.  There was a mass inside it and I was warned that it could very well be cancer.  I had an urgent tonsillectomy and I've been on tenterhooks the past two weeks waiting for the biopsy results.  This morning I rang the hospital and, though I haven't got full information as yet, I was told the biopsy shows no evidence of malignancy.  I won't feel totally reassured until the follow up appointment next week, and still feel very stressy, but I can tell you what has got me through these horrendous past few weeks - support from friends and family, going for long walks on the local park, and diazepam from the GP (I really had to beg for that, as they hate giving it out, but it was a godsend to me.  When the fear became unbearable, usually late at night, the diazepam calmed me just enough to keep going).

Thank you.  Of course only a doctor and tests can give you a diagnosis, but with your history of tonsilitis and being so young, the odds are really in your favour, so try not to worry too much for the time being.  I know it's easier said than done, of course.