Opinions on parent.

Okay so this is long but I would really like answers as to what you would do in my situation. I've never had that great of a relationship with my dad. He's a heavy drinker & married a woman who also drinks a lot so they're constantly at it. He kicked me out when I was 16 because he found one of her shirts in my laundry & has even left me stranded on the side of the road when my head gasket blew up in the middle of the night. We don't talk that much really. Recently my 15 year old brother stopped going to his house because my dad spends more time drinking than he does hanging out with him & he got tired of it. My problem is I'm pregnant. I'm still basically a kid in his eyes I'm only 20. He was really excited to learn I was pregnant but has continued to throw insults at me that I hear through the grapevine when he gets mad. My other brother told me he was recently watching a movie about a father & his kids & my brother walked in on him crying. I got really upset when he told me this because I've always been the one to care too much. Even though my dad pushes me away a lot of the times I feel bad & blame myself. I just want him to act right. It's not hard to get along with your kids. He does things to push us away but cries over things like that & it hurts me to know he's hurting. What I want to know is, should I even keep trying with him? It's like a constant cycle. I just want him to be apart of our lives & his granddaughters life. I know this is long & I apologize. I've just been so back & forth with it all.