hello would really appreciate of someone could give me a bit of advice on here (sorry for big story)

 im 17 years old and about 3 three months ago i had just got into bed and everytime i swallowed i could feel somthing getting in the way in my throat on the right side. it was about grape size and only on one side, i guessed it was a lymph node after about a week or so it went down and disappeared but then about a month later i noticed there was a pretty big hard lump on the back of my head (behind my right ear) it was about walnut size and agian only the right side but it wasnt painful at all just a solid lump so i went to the gp and they wernt quite sure so i was just told to come back in 3 weeks if it hasnt gone so here we are about 1 and a half months after that appointment and its not really shrunk, its went down but not drastically. but another lymph node has come up under my armpit only on the right side agian but this time it's painful and tender to touch its also about walnut size too. 

if anyone has any advise/idea on what this could be or what causes it please let me know. thanks a lot