Poor pixiefish, it's draining enough having 2 kids without anything else on top of it. Zebra, I'm glad you said that about echinacea as I've been taking it on and off throughout pregnancy and breastfeeding. I know the jar always says not to take it but I was sure I'd read a report saying there had been a trial and it hadn't had any bad effect on pregnant women (not that I can find the report now).
I have been taking Nutri's postnatal tablets which include multivits and minerals and other random stuff said to be good for postnatal and bf mums. Plus whenever there's a cold around I boost my VitC intake by 1000 mg 3 times a day, and Echinacea 800mg 3 times a day. I'm not sure what is actually making the difference but I've been able to avoid all the stuff which dp has caught this autumn/winter. (Usually it's the other way round, I catch everything and he stays right as rain.)
However, having said all that it does sound like you have something more serious going on so maybe a blood test is a good idea?