My partner and I have been together for about 11 months. About 2 or so months ago she visited her hometown and returned, having started talking to this one guy for extensive periods of time daily. I expressed some discomfort with this and it caused lots of conflict between us as I was unable to suppress my discomfort and jealousy and she continued to talk. About a few weeks in, I saw a text on her phone about her kissing him when she goes back home. I confronted her about this and she confessed that while she was home she had kissed him and that she wants to make this work and will not be doing it again-she claims that since the first kiss everything had been platonic and that it was just a friendship where she did something inappropriate. She continued talking with him and we continued to figure things out, eventually having a joint-therapy session where we both expressed our desire to make this work. When it’s been good it’s been the best relationship I’ve ever been in, she’s been an amazing partner. After our session I was able to suppress my anxiety enough for us to have a wonderful week together, almost the way it used to be. Then the other day she showed me a risqué picture that she said she took in the morning and didn’t send to me because she knew I was at work. she hadn’t really taken anything like that in a little while so I found that a little weird-of course my anxiety immediately began to wander. Later that day, I saw a text on her phone from the guy saying something about watching a screen recording as well as a winky face. I didn’t say anything about this. The next morning she told me about a dog he had sent her, and she showed me a picture right off their chat. She mentioned there being a second one and I asked to see and she went to check their chats photo history but hesitated and said it was probably on Snapchat and she’d just check later. I found this weird and confronted her about how I was worried she didn’t want me to see that she’d sent the picture to him. She was upset and denied it saying I have nothing to worry about and that she didn’t do that. I ended up going gone and spending the night to myself not really talking too much with her. Today we met up and spent a little bit of time together. I saw on her phone today a text from him that she “loved” on messages that read “I’m thinking of you and h” (it cut off at the h). I’m guessing this means “you and him”, meaning me, meaning she probably talked with him about this situation. She was really worried about me last night because she saw how upset I was. 
I’m just wondering if I should confront her about the text I saw about the screen recording, as I don’t know that anything will come from the whole picture thing. I want to just not worry about it and continue being happy but something about her reaction when I last confronted her just didn’t sit right with me. If something is still going on between them I just want to know. We both want to make this work, and for me I need to know if this is happening. If it is, I want her to just tell me so we can take a break. I’d like to eventually get back with her because again the relationship has been good except for a few things were planning on discussing in therapy together. 
I know this is a huge block of text but I would really appreciate anyone’s input! I’m sure someone will suggest us just splitting entirely but before I can even consider that (if we did I’d want it to be temporary) I’d need some kind of proof otherwise this is all in my head and we have the potential to continue that really good week we just had. 
Please help!!