Advice??? Cheater?

Sarah

So my bf is a great guy he always talks about how I saved him and how much he loves me. We have a great relationship he says he wants to marry me someday. We already act like we are and like we have been together for a long time when we haven't. We talk about everything. We can be ourselves around each other. We met online he said he got it in Tech School for hookups but now that he moved and is living on base he was looking for a relationship and being picky but he knew I was different and we had a connection. However about a week ago my stupid crazy friend created a fake fb and friended him. She was convinced that he is a bad guy cuz we met online. So she had a profile pic of an extremely hot blonde and friended him. (I didn't ask or know that she would do this) He accepted the friend request. She messaged him on fb and he messaged back. She asked if he had a gf to witch he first replied "send nudes" then she asked again and he said "no I don't have a gf" then she flirted a bit saying that was good. After he asked for nudes yet again and she told him no. When she told him no he replied "fair enough so tell me about yourself". Then she stopped and told him off and that she was my friend. He then apologized and said he thought she was a bot or something. He then immediately texted me and told me what happened and sent me screen shots of the convo. He has been trying to make up for it since and been super sorry and sweet and put so much work into trying to fix this. I want to move on however I feel like he may be lying. I trust him but I have a bad feeling that if he had the chance he would cheat because of this. What do you guys think am I over reacting???