I need help with my sex life

My husband rarely ever wants sex, I’ve tried talking with him about it and he just shuts me down. I try initiating it and he pushes me away. This has been a problem in our relationship for a good 3 years now. I don’t know what to do, it seems like he doesn’t ever want to have sex and it’s a chore for him. When we finally do have sex he lasts 30 seconds tops, I’m so frustrated I don’t know what to do. I’ve never said anything about not enjoying the sex we do have I’m always very appreciative of it and I do enjoy it. I’ve never brought up how it’s so quick because I feel if I ever said anything we would never ever have sex again. Please help me.