My doctor thinks that something is going on with my immune system where I am constantly getting all these weird diseases. Like mono multiple times. Chicken pox twice. Adult whooping cough.

This is why I constantly feel down and blah. He's not sure what it is, and I don't know what to think about it. Like, is that it? I'm stuck feeling like crap for the rest of my life?

Any thoughts from people with similar situations?