How can I get over my ex-boyfriend cheating on me?

It's been almost a year since my ex-boyfriend broke up with me after he cheated on me many times. I had found out about a month before, but I hadn't told him I knew because I didn't want us to break up. I used to have very low self-esteem, and I think it might have to do with my dad being an alcoholic. My father cheated on my mother when I was little. I wonder if this pain has to do with that. My ex-boyfriend and I were only dating for five months, but I still can't get over this betrayal. I'm not sure what to feel to get over it: forgiveness? Hate? He helped me financially after our break up by lending me $3000, so I'm grateful for that. I still hate him for what he did and still want him to like me although we're not even talking anymore. We follow each other on Instagram and that's it. I feel like I still need his validation. This is haunting me day and night. I want to focus on my new relationship and goals, but I keep obsessing over this and keep checking my ex-boyfriend's Instagram and Facebook. I feel so bad and keep having nightmares.