He changes during sex

Hi guys 😊 My boyfriend changes during sex. When he is not sexually excited he is so sweet, funny, romantic and gentle (I know it sounds cliché now). I mean, he is the first to talk about cute little puppies and stuff like that! 🐶 But when we start having sex he changes completly. He becomes agressive, wants to spank me and sometimes insults me (calling me a slut for example, which he would never do while being in his « normal state »). He knows me so much! I don’t understand why he becomes someone else in these circumstances. Do you guys have ever experienced this? Should I act like everything’s fine? I feel so weird 😕