I was having a lot of problems like this myself, and my doctor told me to take a Claritin, or the costco brand, everyday, even if Ididn't need it. It seemed like a waste of time, because it didn't work well at all the first few days. But, after about a week, I noticed a huge difference!! I haven't had any sinus infections, I have stopped taking Psuedaphederine, and have only had one cold/flu in almost 6 months. For me that is AMAZING! I totally recommend it. and, they make a kids formula, its one chewable a day. Maybe give this a try just to see if it makes any difference. It is non-drowsy, so it won't make kids cranky like Benadryl when they can't get sleep.
I would certainly see a different doctor, and maybe even a different practice. Also, maybe an ENT. I personally don't think that kids should go to daycare with pink eye if it is still contagious, and yes, the daycare should take care of it, but really I would be upset if my kids were exposed to it at daycare.