a negative person turned into a positive person that now is disappointed and try to look the brightest side.

As a person i used to be a very negative person. I used to fight with my SO a lot, not because I was negative but because of the things he's done and I didn't like. That led to bad memories. But before i tell you about that, I want to say how I got over the negativity. We decided to really work on our relationship and try and I decided to work on myself and be a better and more open minded person and be happier. And of course I wanted to grow up and be more mature. I don't have any experience, he's my 1st. So I started watching a lot of YouTube videos about whatever I want to fix on myself. Anyways, so those memories don't come very often, like rarely, but when they come, they ruin me. I try to not lose what I earned those several weeks, I don't want to go back to my old self because it's not going to be good for me. I like when I'm happy and smile and feel like the world is "mine". I feel more relaxed and calm. I like that feeling. But those memories that my SO and I have is mostly connected to other people. Like 2-3 specific people(girls) that I don't really ever want to see, hear about them or even their names; it bothers me. He knows that it bothers me, he never talks about them but other people do in front of us. Only the 2 of us know why it bothers me. We've fought over them a lot, like A LOT. That's why it has ruined me so much, and those memories don't go away forever. i dont want to remember it .What do you have to say? Any suggestions or advices.