What should I be thinking? I need major help 😰

Alright ladies, I need major advice. So I'm a 17 year old girl that will be 18 on November 2nd. My boyfriend is 18 and won't be 19 until February. In January we would be dating for an entire year. I could tell you everything, but I'm gonna cut right to the point. I have trusted this boy 110% up until about last month. It's not that he has done anything bad BUT, I have so many people posting on my Sarahah saying that's he's cheating on me. I don't think he is, but after this weekend I'm second guessing myself. He used to talk to this girl and he used to have a huge crush on her and I honestly dont know what to think about any of it. She's really pretty (definitely prettier then me) and she's older then me. I know my boyfriend talks to her here and there but this time, I bothered me. He was talking to her on Snapchat and deleted the conversation and I feel like it was to hide it so I didn't see it but he's saying otherwise. I've been through this type of thing before and it was HORRIBLE. I need advice. What should I be thinking? Should I believe him? Should I try to talk to him some more about it? I just need help. I've been thinking about this for so long and now I just need to stop and know nothing is going on. We're a very close couple and we're super comfortable with eachother and we tell eachother everything. He's like my bestfriend. He hasn't done anything bad to prove that I can't trust him but I'm still seriously doubting myself. So ladies, what should I think about this? (These are messages from the conversation we had earlier tonight and I told him to text me Wednesday, he didn't say that on his own) please feel free to ask any questions if anyone wants to know anything else 🤷🏼‍♀️