Cheating boyfriend??

We just found out I’m pregnant. My boyfriend has had some issues in the past with lying and seeing other people but I thought we were past that. Yesterday I seen he was deleting messages from his baby’s mama on his phone and lied start to my face about it. I told him I wasn’t going to keep doing this with him and he could leave. He did, happily it seemed. I haven’t heard from him since. I don’t know what to do and I really don’t wanna go through yet another pregnancy alone...