My answer to is he cheating on me?

This is a comment I got just a while ago:

 I don't really know how to start this, but I just want to get an honest opinion that won't be sugar-coated. I want to know if my boyfriend might be cheating on me. A while ago, I had checked his phone and there were some odd text messages from him to his second cousin. They said: "Can anyone see your phone?" "Ok good. Would you like to mess around on Sunday?" "How long have you been on it? Would you like to do it again?" It seems like he might be cheating on me with her. Unfortunately this is the only piece of evidence I have.
         Am I overreacting, or is this something I should worry about? I've already asked him about it, but his story doesn't make much sense. He did admit to asking her how long she had been on her menstrual cycle. I don't know why he'd need to know that. In addition, I asked his cousin and her story didn't match his. I don't want this to be true, but if it is, I don't want to stay with him. Please just tell me what you think. Thank you

To be honest, it sounds like he is and that he is trying to hide it. I would say talk to him and see what he says if it wasn't for the text "Would you like to do it again?" The cousin's story is probably the correct one and your boyfriend is probably covering it up. If they are similar but with some differences, the cousin is probably failing at covering up for him. It might not be the cousin he is cheating on you with or at least I hope its not.
        What I think happened is he cheated on you with a different girl. He is covering it up by having the contact be his second cousin's name instead. He asked his cousin to help cover for him but they both have different stories sine it is probably a lie. You're not overreacting and this is something you should worry about. He might be cheating. It definitely sounds like it is. His whole story seems off. I think you should ask until you can be sure he isn't lying or when he finally tells the truth. Unfortunately, it sounds like he is and if he is, you need to do whats best for you.

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