Guys answer please: i'm scared that my boyfriend will laugh at my big nipples?

Your nipples sound perfectly normal. They dont even sound particularly large, quite average in size. Though there is nothing wrong at all with larger ones! Your boyfriend sounds like an insensitive lout, if he laughed at a previous girlfriend's nipples. They come in all shapes and sizes, and all are lovely! Only a pathetic lover laughs at someone's body, it's really the height of ignorance. I'd get rid of the guy and get a better one, if I were you, but if you must keep him, then tell him you are afraid to go further because you know he laughed at a previous girlfriend's body. He will almost certainly fall over himself to reassure you. If by any chance he laughs, feel free to laugh and point at his penis, and tell him it's because it's so tiny.