What is your thoughts on this?

My boyfriend has recently been really bugging about . I don't want to do it! For one, it is painful, and secondly, I am a nursing student, so I have enough sense to know that hole is an exit only. Your rectum can lose elasticity, and poop can leak out. Also, you can get fissures. He does not respect that I don't want to. A long time ago I tried to... I even got a vibrator and practiced to the point to where I could fir him in, but he tried to be way to hard, and it hurt. And because I was not willing to let him do it hard, he lost his patience so I said, "this is the last time I ever try this again!". I just don't want to do it! He get so mad and says I don't give "ALL" of me to him. He makes more money than me, and pays more bills, and takes me out to dinner sometimes....so to him that constitutes as him giving "ALL" of him to me, and he can't see why I am not more experimental. He says I am holding back and it makes him mad that I am such a prude. He tells me that he has had it before and wants it still. I am really afraid that this might be the straw that makes me just leave him. There is more stuff, but just the fact that he wants to get pleasure from something that can cause me so much pain makes me physically and emotionally sick. He has even left the house and stayed out for hours over conversations about this that ends it huge blow ups! What is anyone's opinion? Any personal experience?