How many colds is normal?

[lightwind]

My ds (2.9) started nursery in Sept - only 2 half days a week. Plus we do Gymboree once a week. So far he has had a cold (runny nose, fever, sore throat,) and /or ear infection every other week. I've kept him at home every time he has had a runny nose, as (a) I don't want him to be away from me if he's feeling rough and (b) I don't think its fair on the other kids if he's still infectious. But its driving me a bit crazy, because I can't plan anything, and while of course I know it happens to little ones all the time, I feel so frustrated. Been to the GP with the last bout, when he had an ear infection, and he had a week of antibiotics.
Does anyone have any insight...?

I'm dreadful, I don't stay home if DD (18mo) has a runny nose - otherwise we'd never be out! Last year she had a constant cold from December till May.

I keep her in if she's got a fever, or if she's obviously under the weather. Otherwise we go to the toddler groups which are generally where she picks up the colds anyway.