Biological father & contact

My biological dad & mom separated when I was about 1-2 due to the fact that he was and alcoholic and a drug user. During his high, during his drunken moments he became abusive to the point were he had knifes against my moms throat. I'm now 18 never had any contact with him & I have never seen him, I actually don't remember a thing about him. His family never knew where he was or if he was alive. I've always been in contact with his sister(my aunt) & last week she came over to tell me they've been in contact. she gave me his number and told me to call when I'm ready. I'm 18 and 22 weeks pregnant. I don't think I'll ever be ready, But what if he disappear once again and I lose my chance to ask him the questions I've always had? I don't know what to do or what to call and say.... can anyone please help