Advice needed

My boyfriend and I have been dating for two years now. We are only 17. I know he wants to do IT. I don’t think we should do IT but I feel he will break up with me if we don’t. I’ve been told to use a condoms but I feel it won’t work. Plus I don’t want my vagina to get stretched out. My boyfriend has a big dick. I know this bc he sent me a do. He has hinted before that he wants to do it. He has told me his pull out game is strong many times. And I’ve had a few boyfriends before and I know what a good dick is. I don’t know what to do!?!?!