How do I cope with this?

I’ve been in a relationship for 3 years and due to parents causing issues we are currently in a long distance relationship. He has just moved away to start university and has made friends with 1 guy and 1 girl who he lives in halls with. I’m 1 year younger so not at university yet. He has never been the typical “lads lad” type, never had an interest in drinking etc but all of a sudden he goes out every night drinking with this girl and this boy.

I’m struggling with feeling jealousy towards the girl because he has told me nothing about his new friends and obviously because we are long distance and dont get to see eachother, I am jealous that she sees him all day everyday plus they go out drinking at night. He has never given me any reason to not trust him but obviously the feelings are still there for me. I’ve explained how I feel but he just thinks I’m being silly, which I probably am but how do I handle this?