Please Help Me

Well first up I just would like to say hello, I am a 32 year old male and first off this thread is not about me, its about my 16 year old son, me and my son are very good friends and do almost everything together, but when he was 15 he was starting to take drugs, and like many of you when you were young and you experimented, my son started smoking pot, (i smoke pot too so I knew sort of what was going on) and int he middle of the night he came into my room freaking out having a heart attack and panicing etc etc etc, so I drove him to the hospital when I said it was marijuana the doctor was surprised, and he looked everything up and said it was because of not getting enough excersize... Until we got the bloodtest back.. The pot he had bough was laced with methanphetamine. But anyway after all the events my son had depression, and has recently turned to paranoia, he comes up to me every 5 minutes it seems with "something new wrong with him" and everytime he thinks its cancer, so far weve gone to the doctor about every single thing and everything was fine, but recently he had lumps on his neck, at first it started off as 1 and now its a little group, of small lumps under the skin that he said he could "move around or play with", so we went to the doctor and said it is most likely his lymph nodes acting up because of muscle forming on his neck etc etc etc, recently he has calmed down about it abit because he found other lymph nodes on the other side not as big, he has no pain or side effects of cancer, just these lumps but its been 1-2 months and nothing has changed and I am starting not to know what to think of the doctors diagnosis. But anyway I want to know what you all think. Is this serious or just a typical young confused boy thing :p I dont remember problems like that when I was a kid but he has severe paranoia dont forget.

Thanks for your time. And your input is strongly appreciated :)