You're not crazy but keeping up with his social media accounts can make you feel like you're going crazy! (Been there, done that, blocked him for my own sanity!) I suggest that you cut off all contact with this guy. You know he's no good for you because he's a cheater....or at the very least has a wandering eye and has lead you on, right? You deserve SO much better! Don't heal for him, heal for you. Go out there and become the most awesome single person you can be. Another guy will notice.....and the last guy will be missing out on the new and improved you.

Those thoughts of "what if I don't find someone else"....? Well, with your mind preoccupied with this last guy, you're not truly free to give your heart to another. So in a way, you're keeping yourself from moving on and finding a great guy. Give yourself time to heal and you will find someone else.....someone better.