relationship

Mackenzie
So my boyfriend and I live an hour apart and he's younger than me. I always thought I trusted him, but apparently I don't. I've found myself getting mad when I see he's talking to other girls. He tells me I have nothing to worry about and that they are just friends, that he'd never cheat on me. He seems upset that it bothers me he said "you don't like It because you don't trust me" maybe I don't subconsciously. How do I fix it?