He lied to me.... leave him?

an

Me and my boyfriend have been together for 2 years, we have an 8 month old son together. Ever since my sons been born we’ve been off and on, he always gets mad and leaves me and then comes back. Well we’ve been back together for a few months now. On Christmas <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> we were at a family get together, and a girl comes in and goes to him and my son and she said she just saw my son last month. My boyfriend said she was at his moms with him and my son while i went out, and said she’s his cousin and she was visiting from Texas. I knew i saw this girl somewhere before, i knew he added her after we broke up a few months ago but he kept saying she was his cousin and said she’s his moms niece then said shes his dads and other things too but it didn’t add up so for 4 days I’ve been like i know she isn’t your cousin and he’s been going off on me everyday calling me jealous and crazy.. well a few minutes ago he said okay she isn’t actually my cousin i lied about who she is. What do i do... i never thought he’d actually do something like this. He claimed nothing happened but who knows...