How do I get rid of these feelings?

My ex and I (7yrs together) have three children together and have been split up for a year. In that year, neither of us have had another partner or sexual partner.

However, he’s going to a wedding this week and I’m feeling - jealous? I guess? - thinking that maybe he’ll find a partner or sexual partner. I don’t know why I care so much. I don’t love him, and haven’t for a while. Towards the end, we were only together for the kids. So what do I do? 😢