Husband wont stop getting on dating sites

My husband and i have been married since December. Since we've been married ive caught several times talking to other women and men. It wouldn't be such a big deal if he wasn't meeting them on hook up sites. Im terrified im gonna lose my husband. We've discussed what he's doing multiple times but nothing has changed. I really dont know what to do anymore. Any advice on how i could talk to him about this and what to say?

That's one of the problems. He wont tell me why or makes a bull excuse like he accidentally clicked on a email and it signed him up. I dont know what to do anymore