Sleep issues

Okay... so Riley has made the transition to his big boy bed. He has done pretty well with the change. A few times he got out of bed when he was supposed to be napping, but I was quick to discipline, and that stopped right away. The main issues we are dealing with now are he is waking up much earlier than he used too in the morning, and is not napping very long in the afternoon. When he was in a crib he would usually sleep until 7:30 or 8:00 in the morning. This past week he has been getting up around 6:15am!!!! And his naps would usually last at least 2 hours in the afternoon. This week I've been lucky to get an hour. I think the problem is that when he wakes up he just jumps right out of bed because he knows he can. When he was in his crib he might wake up but would doze back off. I have tried explaining to him that he needs to call me when he wakes up and I will come get him, but I don't think he gets it. The morning time change I can handle. It's really not that big of a deal, but the naps...I need him to nap!!!!! I need those few hours in the afternoon to get things done. That's the only time in the day where I can focus and do Corban's school! I really need those quiet two hours back!!!! I'm not ready to give them up just yet!!!