Other girls man

Idk if I'm the only one with this problem but my boyfriend and I could be just chilling then as soon as I leave some girl goes up and hits on him. Of course he declines every time and immediately tells me when he can but still. Like excuse me did you not just see him with me..did you think I was some friend he was hugging and kissing on just a second ago. Clearly he's very happy with what he's got. Like why can't other girls understand that when you see him happy with his girlfriend to back up. I'm sorry but just had to rant. Hate me if you will but that's just how I feel.