frustrated

my boyfriends ex girlfriend (she was his friend first) is coming to town and wants to spend all day with him. he wants too as well because he hasn't seen her. I told him I wasn't very confortable with it and he got super mad at me. he seems to get upset whenever I talk about how I'm feeling. it seems like if I'm not happy or horny then he's mad. I just don't see why he doesn't understand why it bothers me