Our sex life is awful- should I marry him?

I am due to marry the most amazing man in 3 weeks. We are best friends, he is perfect in every way except one. 

Our sex life is awful. It has been for about a year... I have to practically beg him to have sex with me and he shows no interest in me sexually at all.

Our sex life used to be amazing but we both went through rough patches at work and it took a back seat and now we are struggling to get it back. He doesn't seem to understand why it is so important to me that we work this out. 

We talk about everything but as soon as I bring our sex life up he ignores it or gets annoyed. Am I doing the right thing getting married? Is this something we can work out in the future or are we doomed? How do I get him to understand how I feel?