I still check in on my first love

I just wanted some opinions about something. So I’m in a relationship of a little over 7 months and I couldn’t be happier. But occasionally I still think about my first love and will go to his moms Facebook where I know she’s posts pictures of him. I haven’t seen or spoken to him in over a year (besides awkwardly seeing him at his work but that moment was over with quickly and nothing was said). I see he has a girlfriend and he’s super happy but it’s like an itch I have to itch when I want to check up on him and what him and his family have been up to. I loved the guy and his family but he broke my heart so badly. Why do I keep letting myself see what he’s doing but it’s been over a year? How do I stop?