You're not one to joke about sex: it's a serious subject you don't take lightly. You can't separate sex from love: the two go hand in hand. This doesn't mean you're frigid - each to their own limits - but you're offended by certain sexual acts you think are dirty or degrading.
Advice for you: Try and communicate with your partner more, depending on the rhythm of your desire, and let go more. Try and conquer your body and his slowly, and you'll discover new sensations to share. Your natural reserve and modesty are stopping you from experiencing and enjoying part of the thrill of sex.