I [20M], relationship ended with my gf [19f] due to me going out with a different girl. Need help

Hello, I had been in this relationship for about 2 years in total. Me and my gf/ex parted ways after we both weren't happy about a year ago. The relationship ended because of my partners anxiousness about me. She would ask for me to unfollow people on Instagram that I had been friends with for years and also very much didn't like the kind of music that I listened to. I would do the things that she asked and I still didn't feel like I was gaining any trust from her. Anytime I would try to talk to her about doing those things she would say that they made her uncomfortable and that if I asked her to do it she would do it.

About 8 months ago we started talking again and eventually we started dating 2 months after that. At the beginning of this time I had a friend that was a girl and we went out to eat as I thought it would be okay because we we're just friends. It turned out that the girl liked me and instead of me cutting her off, we went out again to eat. After going to eat we never spoke again and stopped being friends. Yes I did this while in a relationship. I felt extremely guilty during it and I had immediately knew that I had messed up.

During the relationship she would still ask me to unfollow people on Instagram and try and get me to throw away some albums that I used to listen to. During the relationship she was still a little anxious just not as bad as it was before we broke up the first time.

I know I am giving examples of bad parts of the relationship but this happened only about 20 - 30 % of the time. I really did have strong feeling for my ex and hadn't stopped regretting about going out with that girl, it was just so dumb.

Now in present time about 6 months since I went out with the girl. My ex found out about this and ended the relationship with me. I know I deserved this and honestly I just don't know what to do. Should I try to apologize again or just never speak to her again.