The happiness that he brings you is only a superficial happiness. But he's simultaneously making you miserable and guilty because, unlike him, you seem to be a nice person and obviously feel uncomfortable on behalf of his gf. I know it hurts now, but you would be much better off without him. Stay strong with the no contact, you're doing very well! Like someone else mentioned, call up a friend, come on here to vent, or do something else to distract yourself whenever you feel the urge to call/text or otherwise contact him. He does not deserve your regard in any way, shape, or form. You can find happiness in other things, trust me. You just have to be willing to look hard enough. And there will be a guy who will make you smile and laugh and who will not toy with you like this guy is. There will be a guy who will respect you and treat you as you deserve to be treated.