You stated you are giving your 150%. You are giving that TO him. Save some for yourself.
What is he giving to your relationship? At least he is honest with you but the direction he is taking is stepping back from his marriage.
Please don't take this the wrong way, but it sounds like you are very co-dependent in your relationship.
1) Try to do things that take your mind off him. Be yourself, and LOVE yourself first and formost. Join belly dancing classes with friends or make a new friend. Better your heart and gain support from friends and family you trust. (as hard as this may be its important that you strengthen up).
2) Be willing to experience whatever happens. That last statement is MUCH easier said then done. So thats why the first step is so important.
It may just be that once he sees you're doing so well on your own, and not stuck in a cycle of NEEDING him so much emotionally, perhaps he will wake up and realize what he has lost!
Has he moved out?