No longer sexually compatible

I could have sex at least twice a week but my husband can go several months without. The last time we had sex was three weeks ago, after having 5 months between then and the previous time we had sex. This has been going on for the past 3 years (has progressively gotten worse.) We have both been very distant with each other lately and I’m spending most nights sleeping in our bed alone because he crashes on the couch. I don’t know to do. I feel like I’ve lost the version of my husband that I married.