please, i desperately need advice

My boyfriend of 3 years is a wonderful man but we have continued to have terrible sex since the beginning of our relationship and recently ive been getting a funny feeling. for example he hasn't even yried to have sex lately (he is fine with our sex life im the one bored) i texted him a really nice text the other day because he was having a bad week and he totally blew me off. i asked him about it and he said "he was just in the wrong state of mind because hed been drinking " which is really unlike hom and i know its probably not that big a deal but i just have a weird feeling and i know he plans on proposing soon so i just need to get my feelings straight and im looking for some guidence.