My son did the same thing. I was due with my daughter on his 3rd birthday, and the only thing I wanted was to have him out of diapers by that time. We started a few months before he turned 3 and within two weeks he was trained. It was amazing and too easy. Everyone kept telling me he would regress about two months after the new baby was born. He did great up until my daughter turned 3 months old. He started to wet the bed at naps and at night. During this time we were traveling quite a bit so I thought it would get better after we got settled into our normal routine. It didn't, he actually decided not to aim when he went in the toilet (got on the walls and floor) and he also thought it would be neat to aim it into the tub. That didn't last too long due to time-outs. So on my daughters last well-baby check I asked our ped about it. He said it was perfectly normal. That they are now getting into the phase that they are sleeping deeply and are not waking up as easily and that while awake, they don't want to take the time to go to the potty. He said to make him go every 2 hours, and to put pull-ups on him at naps and at night. He also said to watch and make sure he is having normal BM's due to the fact that they don't want to take the time to do that either and will get themselves constipated. We aren't having any problems with that thank the Lord!! So, I would say that your son is just as normal as mine!!! At least by my ped's advice!