Definitely try another Doc because it's better to be safe than sorry, I think nobody knows your body better than YOU and if you think something is off then keep looking until you get an answer that eases your concerns. BUT if you think you're just getting sick a lot because you're run down, not enough sleep, stress, etc. then try what I did: VITAMINS
! I used to get sick a lot and I don't think I've gotten a cold all year. It can be expensive and a pain in the butt, but this is what I take: 2 gummy multi vitamins, 1 vitamin C, 800mg vitamin D, slow FE iron, 2 fish oil and 2 flax seed oil. I swear it has made all the difference for me. I also religiously use Zycam if I feel something coming on. I'm talking 4 or 5 a day for 2 or 3 days when I feel a little sore throat coming on. (Knock on wood) but this regimen has worked for me for a year!
As a side note...if I ate a little better, maybe I wouldn't need all those vitamins haha! I really do try to eat well and get in my fruits and veggies, but we all know how well a balanced diet fits into nursing school (NOT)!!!