How to build a better relationship with estranged father?

My parents divorced 10 yrs ago. The divorce was just a little messy. I have been living with my mom. Up until about five yrs ago, my dad and i had a decent relationship. But When I think back on some of the things he's done, it makes me so upset. I love him naturally because he is my dad, but at the same time I feel like I just want to hit him. Due to the stress caused by this among other things, I am now dealing with depression. I was even once put into psychiatric hospital for suicide attempts. I want a better relationship with him, but I just can't seem to forgive him. What should I do?