hurtful relationship??

Ok, so to start off I've been dating this guy for a year & about 2 months. When I first met him, I wasn't really intrested in him and he was , so I told him I'd rather be friends take things slow & see how it goes. Thought that time he was so sweet, we would hang out he would have his little surprises. Also, he told me he had an ex & a baby with her, and I said that's not a problem.. so when we finally got togther things were good his family liked me & still does to this day. When we were about like 4 months into the relationship he left me for his ex for about 1 month.. he said because he wanted to spend time with his daughter and not to mention his ex is those immature moms that in order for him to see his kid he has to be with her. So he then came back to me I took him back & we did good for 6 months & then he left again that's when I found out I was pregant. He would push me at times & yell at me and blame stuff on me that I didn't have fault at.. when I told him I was pregnant he was happy but I told him it be better if he did whatever he was doing & I did whatever I was doing. But somehow we needed up back togther.. we been arguing a bit & last night I tried talking to him & he told me if I didn't move he'd hit me.. idk what to do I'm only 18 & 11 weeks & 2 days pregnant he's 21...