It is frustrating I know, I have been having the same battle this year, my DD and I have been hand balling colds to each other I work in long day care and DD attends full time so we are constantly exposed to things.
It will get easier your DD's immune system will strengthen up, DD and I got sick the year I returned to work, last year we only had minor colds but this year I think I've been more succeptible due to being PG and under stress and a little run down.
DD seems to get over things a lot quicker than I do and has been still eating and sleeping well despite a green nose and cough
talk to your GP if your not sure ( I don't know about where you're from but most of the gp's here blame childcare for it anyway)