Certainly hasn't worked that way for me Ladylove. I've never been so sick as I have over the last 14 odd months while breastfeeding DD3. I've had pneumonia twice, every single cold going and a bout of really severe gastro (which I never normally get). My DD3 has also been really sick on a number of occasions so TBH I'm having my doubts breastfeeding does anything for immunity!

Maybe for you now its just a case of pregnancy together with looking after an active toddler taking a toll on you.