I still get jealous..

I dated my bf for about 2 years and we broke up. He started dating someone else pretty soon after. When I decided it was time to cut ends with him, he broke up with her to get with me again. Of course I gave in but I still get jealous. He doesn’t have her on social media because she blocked him, but when her friends post something where she comes out, he’ll like it. Yesterday we went to an arcade and she was there. I’d notice him look around often and ofc the first thing I assumed was he was looking for her. Then, she got on top to do an activity and he would occasionally look up at her. Idk what to feel/say but I don’t want to be a second person.