Why don't me and my boyfriend talk as much?

We talked all the time before we went out. Like till 5 am and its just weird. Cause ever since we started dating hes always 'gotta go.' He doesn't say i love you anymore either. We started going out on Friday. But before that we talked all the time. He says he tired when ever I call him. I know hes not cause his sister says hes been sleeping allot more. But I can barely talk to him now. When he says gotta go i usually say "Okay, bye I love you. " Then he just clicks. I really don't know what I'm doing wrong.