relationship trouble

okay so I’ve been dating this girl for about 3 months. We argue and have our ups and downs, but we’re happy. We just struggle with communicating our feelings sometimes. Sometimes she’ll say stuff about how she doesn’t trust me, but she’ll turn around and have guys at her house or drinking. She expects me to trust her with that after one of the guys kissed her. I trust her, but she doesn’t trust me and I’ve given her no reason not to. She also will do this thing where she holds stuff in. She just won’t say what’s wrong. She’ll say “I’m fine.” Or “I don’t want to hurt you with what I have to say.” Or just a “I’m sorry.” I don’t know how to respond or what to say anymore and I need some advice because I don’t know what to do. I want to make it work, but it’s so damn difficult.