I can't have an orgasm and have very little sex drive. I am frustrated and think I would enjoy sex more and

In my 20's, married have been together for several years. Good relationship, not a lot of fighting. Have tired to masturbate and finish but no luck, I feel like I could go one four hours and I get close but never finish. Want to have a great sexual relationship with my husband... but not sure how to fix this. Hope I am not the only one with this problem.