What to do when your man doesn't want it.

So I need some womanly advice. My man and I have been with each other for the past 3 years. Within the past 5 months he doesn't seem interested in sex. I don't think he's cheating because we live in a small town where we know everyone and I would surely know. But it's not like I'm not trying to spice it up but seriously I don't know what to do. Yesterday I asked him for a kiss and he wouldn't because he was so concerned with facebook on his phone and I told him it was just a kiss not like I'm trying to force him to making love with me and he told me "well you already did that last night." But the thing was I didn't force him into something he has the right to tell me he doesn't want it but still, ouch. What to do?..