Boyfriend has been acting different after getting back together?

So here is the thing im 38 weeks pregnant and due any day now. a few weeks ago my boyfriend/baby dad broke up and we got back together last saturday. from june 30 untill now he has been hanging out with his friends all the time. alot more then he use too! so saturday we went to the movies and he was texting and he was kinda putting his hand over his phone when he was texting. then last night when he came to my house he turned his phone off.then today i asked him if he was gonna stay the night with me again and he said he couldnt because he had to work in the morning. he usually has wensdays off he said that he had to work for someone else. before we broke up he didn't use to hangout with his friends alot. is was like every once in awhile. he didnt use to try and hide his phone and he didnt turn his phone off when he came to my house he also would still stay the night with me even if he had to work the next morning. so i was texting him and i told him that i was gonna go he said okay usually he asks why i dont wanna talk to him but this time he didn't. and when he hangs out with his friends he never asks me to go. one of his friends always has his girlfriend with him but my boyfriend never asks me to hangout with them. could this be a sign that my boyfriend is seeing another girl? he also made a facebook and hasnt added me or nothing.what should i do? thanks