How to boost immune system?

Hello,
I am just wondering if any of you have suggestions for how to boost my immune system?  I have always been prone to getting sick, especially respiratory infections, and now that I have a baby I am catching everything he brings home, plus being rundown on sleep from him being sick.  In the past 2 months I have had bronchitis twice and pnuemonia once.  I also have asthma in addition to Thal minor.  I take Omega 3 natural fish oil, Ester C and my asthma medications (Albuterol and Advair), I was not taking my asthma meds up until I got pnuemonia because my breathing was doing very well previously.  Otherwise I have been trying to eat a healthy diet, but lately it has just been soup and crackers.  I work full time as a school counselor so I get exposed to all sorts of stuff at work too. 

Thanks for any suggestions!
Crissy

I would suggest getting your vitamin D level checked. Low D levels cause tiredness and weaken the immune system. In addition, most people tested find their levels are low and need correction.

you might also see an ENT, I don't have thal, my kids do, but I used to get lots of upper resp. infections, like bronchitis, and recently found out I had very narrow sinus passages.  do you also have chronic sinusitis? I used to wake up totally congested every morning, but usually cleared up after a hot shower unless I had a sinus infection, which was 4-5 times a year. I had sinus surgery 3 yrs ago and have only had 2 sinus infections and no bronchitis since then. it was a very easy, fairly painless procedure, and I had lots of puss and infection stuck chronically up in my sinuses, my doctor said anatomically I needed that surgery. oh and I had a deviated septum. 
good luck, hope you feel better soon!