My boyfriend has been pulling away emotionally and pulling away with his time as well, yet continues to talk marriage. If that isn't enough to raise my eyebrows and concern he has changed sexual behaviors like latly he has dominantly preferred me on top, and tonight he pushed me off and started masturbating and still didn't get off. He has never pushed me off him and he has never ended in masturbation. All I know is it left me confused and feeling used.

Something's going on.. but you are going to have to get him to talk otherwise all anyone doing is guessing. And it can be any number of things going on... or a combination of them.

it sounds like he may be experiencing some physical problems he doesn't want to talk about (you on top, trying to masturbate to finish unsuccessfully) - he may need to talk to someone or see a doctor. However, I notice you say "cheating... AGAIN"...

Your relationship needs some help - and you need a voice and some self respect if he's pushing you off, sexually demanding and cheating. Speak up for yourself, communicate and value yourself - no guy is going to do it for you.