DB not nice when they are sick so little I agree with Cassius, keep fluids up, which you will anyway as you are demand feeding. He's probably sleeping more fighting it off. If he gets a temp get him checked seeing as he's so little. If you feel he's not feeding as much try offering an extra feed here and there.
DS is nearly out the others side of her cold now and handled it pretty well.

If he has trouble feeding with nasal congestion you can use a snot sucker(for lack of the correct name right now ) to clear him out a bit. Vaporisers are good too.