Boyfriend has no interest in sex

Ok...so my 29 yr old boyfriend whom I've been with for 7 months has a low libido and I have a high one. We've gone over two weeks without sex now and I'm going crazy. He works outside 40 hours a week and with the below freezing temps we're having, he's just wiped. Should I give him the benefit of the doubt or do something about it? He's had a low libido the whole time we've been together, but this is the longest we've gone. His brother's girlfriend told me that his younger brother is the same way. Wondering if it just runs in the family...