Question???

Hi, never used this before but I need some impartial advice.My bf and I have been together over 4 years, we own a place together and are happy. We are both in our late twenties, the only issue is that we haven't had sex in over a year. I have a higher sex drive than my bf and would be happy having sex daily. He seems happy to go without/doesn't seem to see me sexually at all, we rarely kiss etc. I have bought it up on many occasions as I think I'm too young for a sexless marriage! I'm worried if it continues I may stray/suggest an open relationship.Any advice appreciated!