Help with the games guys play?

Ok i have dated this guy off and on since middle school i am now 20 but here's our history... every time we dated he'll get close and then pull away and we wont speak for awhile then he just reappears and we go through it all over again the last time we dated he told his mom he was going to ask me to marry him but then disappeared i know i need to move on and i have tried but he just keeps showing up and i wanna know why anyone have an idea