You don't have to say you want to wait until you are married unless you want to, but you could certainly tell him that you (and he) are not ready; for what it's worth, you could also tell him that it's against the law. Incidentally, football refers to a platonic (not plutonic) friendship, which is maybe not what you want. A platonic friendship just means you are friends, not boyfriend/girlfriend. You can still be his girlfriend, date him, kiss him, etc, without having to have sex. Tell him that if he cares for you, or even loves you, then he will understand and respect that, but please don't let him blackmail or pressure you into doing something you don't want to do or will regret. You'll need to be strong and true to yourself, but it will be worth it.