It sounds like he could be depressed, maybe with low self esteem as well. Or he could be getting it elsewhere (or thinking about this), but doesn't want to move on out of committment / obligation / deep routed but dissatisfied love.
He's probably as unhappy as you are, but shows it in a different way - and doesn't understand or know or want to talk about his feelings.
I've been with a glass half empty partner 23 years, who has no dreams or desires or ambitions... still don't know what to do about it, so ultimately have decided to get on with my life in my way, and he has the choice of keeping up with my pace or moving on. The funny thing is: the happier and more enthusiastic I am with what I am doing - the more attractive he finds me, the more he see's the old me is back (the one he fell in love with), the less inclined he seems to want to move on / leave!
(And I'm not yet financially set up to move on by myself, or ready to get into a new relationship, so sticking it out is convenient for me for at least a little while...)
OPEN HONEST NON-CONFRONTATIONAL COMMUNICATION about how you are both feelings, esp his feelings/worries, is the most important thing right now. Don't confront him with playing away, or accuse him of depression, just go softly softly - be his friend for a bit...