What Happened to My Perfect Little Sleeper?

Aiden started sleeping through the night at about two months. However, since he has started daycare, he has been waking up multiple times during the night. I try to just rock him and get him back to sleep, but the minute I lay him in his bed he wakes up. Last night he woke up at 12:30 am (thanks Daddy for taking care of that one), 1:45 am, and 4:30 am. Needless to say, I am dead tired today. I assume he is just adjusting to a new schedule. I really hope he gets over this phase soon before Mommy goes nuts!