No, you don't know the "real" him, you only know the "him you wanted him to be", it's an illusion. We never "can" change another person into what we imagine they "could be", they either are or they are "not". You fell in love with the "idea of him and you being in a picture that doesn't really exist".

Yes, this takes time to grieve and get over, yes it is like withdrawing from a drug addiction too. Seriously, if he is content/happy away from you, it was never really "love". It is just as well he doesn't come back, you don't want to wake up someday with two children and being very unhappy and wondering what the heck you did because now you can't stand him and you are "stuck". It's an awful feeling because chemical high actually eventually fades anyway, so if the other person is the wrong choice, the whole thing can be miserable.

I understand it is tough right now, but this "will pass", move on dear and find someone that may actually "fit" better.