My 15 month old keeps waking up at 2 A.M. why?

My 15 month old has a bath at 830, bottle, then to bed and asleep by 930. Everynight he wakes up around any where from 2-2:45 screaming and crying DA-DA DA-DA.. i go in and try to lay him down but he gets back up and is crying histerical so since my husband works 6 days a week a 7-7 shift i just sleep in the living room sofa bed and my husband stays upstairs in our room. I want him to sleep through a full night so i can sleep a full night with my husband! I don't think it's his teething because most of them came in except the back ones. Is there any certain way to try to get him to sleep through the night?