Military relationship advice

Hi so I need advice on what to do, my boyfriend and I are currently in a long distance relationship. He’s the military stationed in San Diego while I’m studying here in our hometown in Florida. We’ve been having troubles lately in relations to a girl he hangs out with. I don’t know if I’m overreacting or if it’s something I need to be concerned about. I’ve been dating him for 4 years now. I’ve always been okay with him having female friends, etc. I trust him with everything and I’ve known him literally since we were kids that’s how much trust I have. But getting back to the point, he has been hanging out with one specific female friend a lot, which rubs me the wrong way for many reasons. About a month ago, he had sent me a photo on snapchat while at her house, and I noticed his stuff that he had previously told me he was going to keep at his coworkers house was at her house. So I confronted him about it, he said she’s a close friend and that’s why he decided to keep the stuff at her house. So I asked him why lie about it if I wouldn’t have an issue with that. He said he felt as if I would get upset over it. We talked about it and moved on from it. Last week, he sends me a photo through snapchat in a bed that wasn’t his bed. So I confronted him about it and he said yes he was hanging out in her room watching tv, laying in her bed with his dog (she’s currently taking care of his dog because he can’t have the dog in the barracks with him. Which I was fine with in the beginning. He just adopted this dog about two weeks ago) I told him how I felt about him being on her bed, I told him I felt it was disrespectful and also made me feel uncomfortable. It just didn’t sit right with me and he said that he was cuddling with his dog and nothing happened and that I’m overreacting because she’s a good friend to him. We had a talk about it and moved on, but today he sends me photo through snapchat of him in her bed again today after not replying for an hour (usually when he doesn’t reply for long time is because he’s taking a nap so it didn’t bother me until I saw the snap he sent me) So I confronted him about it, he said he was taking a nap on her bed with his dog because he was tired. Mind you he never even communicated he was going to her house or on the way to her house to see his dog or anything. So we had a huge fight about it because I told him I feel like he’s overstepping the boundaries and it doesn’t make me feel comfortable at all. I told him I don’t mind If you hang out with her either way his dog is at her place, but I don’t think it’s right for my boyfriend to be laying or taking naps in a females bed. A female I don’t even know. So his response was that I’m overreacting and that I shouldn’t be overreacting. He’s currently still at her house doing his homework.