You have the right to set sexual limits and to communicate them. If you don't like what someone is saying or doing to you, tell them how you feel. Be very clear and assertive. You have the right to be rude and aggressive in a threatening situation. It's very hard to always be the one to offer yourself.
Some men are afraid that women say yes, but mean no.
Men don't like to pretend that they always want sex. Men are afraid of being rejected and turned down. Women Women are socialized to believe they should always go along with what men want, in spite of what they want. Many women are afraid of hurting men's feelings. Some women don't like pretending that they don't want to have sex.