My son is driving me insane. How old when they start to teethe? He only wants my nipple in his mouth…

My son is driving me insane. How old when they start to teethe? He only wants my nipple in his mouth to feed and chews on it. My nipples hurt so bad... He won't allow more breast in his mouth; he lets it out and just sucks onto my nipple. Then he doesn't want a pacifier. So hes screaming next to me right now. There's nothing I can do for him. My nipples aren't dog toys.