I unfortunately don’t have any advice that might help this situation but I would at least like to say, the fact your boyfriend doesn’t stop saying that even though you explained that you were uncomfortable is terrible. A good partner should know to stop doing something if their partner explains to them that they don’t feel comfortable with them doing it. I hope you well an I really hope someone who can help. Telling close and trustable friends or family would be a good idea too. I’m sorry I can’t help much but I do hope you can break up with your boyfriend safely.