I'm heart broken and don't know what to do!!!

ELl • 💦💦💦
So a few minutes ago I got a message off a girl only a year older than me saying my boyfriend wanted to meet her, she obviously said no but he's trying to tell me it was because she wanted some weed a while ago yet she's saying the opposite that she doesn't and she's never spoken to him before! It's broke my heart as I'm always hearing things! I'm trying to talk to him but it's just arguments and I don't know what to do! I love him but hate him at the same time! Who do I believe ????
Please help