Anybody who helps you and later request that you pay back might have done so because of your body in the first place. He wouldn't have helped you if your body did not attract him. Such a person is worst than a beast. If you have such a person in your life, it is better you break up from the relationship.
After breaking up, then look up to God to meet your needs. Phil. 4:19 assures us of God's supply. God says He will supply all your needs and not some of them. As you depend wholly on God, He will make a way to get your needs met.
Never subject yourself to such a cheap blackmail!