If you keep asking him over and over again and he doesn't do it until you're at the end of your rope, then it sounds rather abusive. Unless you don't express yourself enough to him until you just can't hide your anger and sadness anymore. Direct, honest communication is key. Ask him why he doesn't want to have sex with you until you're at the end of your rope. Try to develop an open-ended honest discussion, not just accusations. Tell him how YOU honestly feel, using "I" in your sentences.