He has said he is not happy in his marriage, dull homelife, nothing in common, living as friends.
This is classic pre-shag preparation.
He wants to have sex with you, keep it secret from his wife, stay in his lovely marriage where he has a family, and all the comforts of home.
Don't believe he's not sleeping with his wife, they all say that.
He will sleep with you until a) you bore him b) someone better comes along or c) he is found out and goes grovelling back to his wife.
None of these outcomes will be good for you. End it with him, he is married. End your own relationship, you don't love or respect your partner.
Work on being on your own for a bit, build up your self esteem so that you don't fall for this crap again.