Help!

Jennifer
So my so and I have been together for going on 5 months.  We've known each other for 10 years.  We've always had a huge attraction to each other but due to bad timing we were never able to act on it until now. Needless to say I've always known that he was "the one". Call me crazy lol 
So our first few months together we couldn't keep our hands off of each other. We literally had sex multiple times a day.  To say our sex life was phenomenal, is an understatement. 
Well for about the last 2 weeks,  I can barely get him to look at me.  We've had sex 2 times in a three week span.  I'm so confused and it's killing my self esteem. I've talked to him about it and he claims to just be tired,  but Idk.  Help please!!