Is it normal that my boyfriend sucks on my lip while kissing?

My bf likes to do this too and at first I didn't really like it. It felt like he was trying to chew my lips off. But in a way now it turns me on more and I really like it. Maybe just tell him that when he does that he needs to not do it so hard because leaving a hickey or something on ur lip is not good and he is doing it too hard. So I would just be like, "Babe I love when we kiss/makeout and sometimes when we do you suck on/bite my lip and it hurts and leaves a mark. I don't like this but I do enjoy kissing you. Could you maybe lay off on it for a while or just not do it so hard?" He might not even know he is doing it that hard so I would just say what I previously said and see what he says and let him try again. Or you can show him and do it on him. That is fun too. Hope this helps. :)