Most Helpful Guy
You two aren't in a relationship and from what you say it's a good thing too!
You have every right to be on a dating site and shouldn't feel that just because he's there doesn't mean you can't be. Just try to stay out his way and do NOT go back on his social media accounts, it will only spell bad news
Most Helpful Girl
1) Change your locks.
2) Date online anyway. His dating life doesn't matter anymore, and it is irrelevant to your dating life. You should be able to block him on the dating site, so if he bugs you, block him. Otherwise don't concern yourself with him.