Is it worth revisiting?

I keep thinking of my ex. we dated almost 2 years ago now for only 4 months. We broke up bc we were both going through really bad mental patches and we were becoming way too codependent on each other. I was still in love with him for months after, and i didn’t reach out because i thought we’d be better without each other. I’m still friends with his sister and shes casually told me he’s really turned his life around. he transferred to morning classes at our school so we see each other all the time and he just followed me on social media. I can’t stop thinking about him and I’ve been so tempted to reach out and ask how he is. I don’t even know why I keep thinking of him because I’ve been in a relationship since him that lasted longer than ours even did. Ughhh idk what’s wrong with me. I’ve been having dreams and everything. Feeling rly conflicted and just needed to get my thoughts out.