I feel you OP, it's happened to me several times.
Many wankers will say variations on the classic line of 'my wife doesn't understand me'- a recent variation seems to be to say they have a sexless marriage by the wife's choice. You do not know this- probably it's all lies. It's designed to make us think their actions are marginally more justifiable or something. My one said his wife 'declared herself asexual' and even said he endured it for ten years before he began to seek out a sex life for himself. He didn't mention it to her because he 'didn't want to hurt her feelings.' He really sold this to me! I was a shmuck.
My mum made a good point 'a man for whom sex is so important wouldn't put up with a sexless marriage.' So, it's highly unlikely.
They will even message you a lot to keep stringing you along. We're just ego strokes to them at the end of the day.
If it's anything like me, you feel very lonely in the times when he's not in touch. Really raise your awareness of those times- times when he's not available to you, he doesn't give you the emotinal support you need, it's clear you're second best, he does the bare minimum etc etc. Notice the gaps and the treatment that shows he only gives a shit when he wants to.
It may be that he even spends hours or occasional nights with you- but if you think about it you can also see all the times he isn't there.
Very occasionally, these blokes will leave their wives for you. This happened to me once but it was a mistake for me for varius reasons.
Maybe it'd help to tell him how you feel, if only so you can get it spelled out again from him that he's not planning to leave his wife for you or anything? That might help you move on. You honestly don't have much to lose.
But to me it was spotting the gaps, the times he wasn't there for me, the ways that there was little emotional intimacy even as friends, that helped with the latest one- that and realizing I was being used.
Don't get me wrong, he put on a good show of caring for me- when he could be arsed.
Just looked at your username 'Sosounhappy' 
. He's making you miserable. And he's a user. Walk away xxx