Thanks for the query to H.C.M.Forum.
One, thing I want to make clear that this unilateral enlargement of tonsil
is not a cancer .
The history ,which you mentioned is absolutely different.
Now you stated that there is difficulty in breathing ,when you sleep ,on right side.
Just due to compression ,nothing more than this.
Consult an E N T and get in throat swab and culture will reveal the nature of pathogens and take treatment accordingly.
Hope I have answered your question.
If further any question I will help.
Get well soon.