How can I boost my immune system?

First of all i get sick very often. About every 5 weeks. Not too sick but it’s uncomfortable and makes it hard to do things I normally do like go to school or work out. I take vitamins, I eat healthy, as in make sure I eat enough protien, fruits (apples, all kinds of berries)and green veggies everyday etc.I wash my hands all day throughout the day, i carry hand sanitizer. nothing helps. I actually had to get my had to get my tonsils taken out in february because they were at an abnormally large size for about a year. I know the surgery wasn’t suppose to “cure” me but the Dr. said it was suppose to help. Whenever i am around someone sick i am extremely careful to not get too close, not touch stuff they have, wash my hands if so. I am also always usually tired, even when i sleep 9 or 10 hours.
Anyway, can anyone recommened something to help. I cannot live like this anymore it really is a weakness. Any advice will help. anyone know something i can take? specific vitamins? superfoods? natural remedies?
thanks so much