idk why am i like this

I (24F) and my partner (25M) are in a long-distance relationship, and I'm not sure if I'm overreacting, overthinking, or if my feelings are valid. Yesterday, we had a huge argument because he’s been talking to this girl a lot lately. He insists that she’s not into guys, but I can’t shake the feeling that something is going on. He mentions her to me every day, and it just feels like he’s getting too close to her.

I know he’s friendly, especially since he took a break from school for a while and recently returned, making a lot of new friends, including girls. But I’m starting to feel like he’s not respecting me or our relationship. He even showed me a screenshot of a conversation where he and this girl were playing a “smash or pass” game with their classmates. He was the one who suggested the game, and they both agreed that just talking to someone doesn’t mean there’s something romantic going on. I was really shocked when he said he found it “annoying” that people assumed something was going on between them.

I’ve told him that I’m okay with him talking to other girls, as long as I’ve set my boundaries, but when he talks to her about inappropriate stuff, it really hurts. He says it’s normal for them and how they talk, but it feels disrespectful when I express my discomfort. We got into a fight, and I reminded him that we started as friends, and their conversations remind me of how we used to talk when we were just starting out.

He says he’s just excited to make friends, and I’m happy for him, but I just wish he would respect my feelings, our relationship, and my boundaries. I don’t expect him to stop being friends with girls, but it’s hard for me when I feel like he can talk inappropriately with her and dismisses how I feel. I told him it was not about jealousy anymore but respect.

Before this argument, there was also an incident with his girl best friend. I was on my way home from work when he told me he was going to her house with her cousin, who’s a guy. Later, he told me the cousin had to leave, and I was confused because he was late getting home. When I asked him if it was just the two of them, he mentioned her sister was there too, which shocked me. Maybe I’m overthinking, but he liked that girl years ago, and I can’t help but feel uneasy about the situation.

I don’t understand why he makes me guess things like this. How am I supposed to know if he’s telling the truth? After all of this, I feel hurt, and I don’t know if I can fully trust him anymore. I think it’s causing some trust issues between us.

what are your thoughts about this? need your advice.