... have you been declining sex recently?
In other words, has he been initiating it and it's just the wrong sort of time, you're too tired, a bit grumpy and just not felt like it.
You don't have to have said no, just moved away.
We went through a phase of that; I felt I was getting knocked back all the time, so I stopped asking/initiating. Yes, it was difficult, but surprisingly enough blokes, particularly older ones can do that.
It took weeks, but eventually she asked if we felt like it. To my shame, I said I had for weeks, but not tonight. After another couple of weeks 
we sorted ourselves out.
tbh, as the others have said, physical attention is the best clue; kisses, more kisses; holding him to you while you kiss him. The in the bed stuff should work.
If he declines, give it another shot a day or two later... if he declines a third time - sorry, you will have to talk about it.
[if he's doubting his sexual response, possibly the little blue pills would help. I've used them occasionally and they are a wonderful confidence boost. For both of us :0]