I hava a hunch that this guy is not your boyfriend. If he was your boyfriend, he is not going to harass you for sex. A woman who loves her boyfriend does not need to be harassed for sex. It will be a pleasure to make love with him, not to have sex.
So if he is not your boyfriend and keeps doing this to you, just tell him that if he won't stop, you are going to report him to the police and get a restraining order against him. You don't have to take this treatment from him.