My bf uses this against me

My bf has been upsetting me lately. He’s been bringing up something from the past that I did that really made him mad at me.

When we first started dating, my ex bf (who I was with for 5 years but it was a toxic relationship) called me one day and asked me if I could pick him up from the hospital. I picked him up and took him home. And then I stopped talking to him. I was just trying to be nice and be there for him in a time of need. The day that I did that, I immediately told my current bf about it. He was upset with me for a while.

I told him that I was sorry and I wish I never did it because I never wanted to upset my bf. He told me that he forgave me. We moved forward.

We now have been together over a year and a half and we live together.

Almost every single time we have any argument over anything, he ALWAYS brings up that I picked my ex up that one day. I have told him that I don’t want to fight about that for the rest of my life. I thought we put that to rest.

Also, if he does anything to make me mad at him, he uses that against me. To try to get out whatever he does to make me mad.

Today randomly he brought it up. And we weren’t even arguing.

Idk what to do to make him get over it. I definitely proved to him that I don’t want my ex anymore, I haven’t talked to him since the day I picked him up, I try so hard to be a good girlfriend to my current bf. I don’t want that to be used against me for the rest of my life. It’s not like I cheated on him. But I do understand why he was upset over it.

Any advice ladies ????