Need to get my mind straight

I need your ladies advice.

Here's a backstory.

My boyfriend was an addict and I as well but we have been sober for a while now, I almost 2 years and him 7 months. During his alcoholism he was talking to other girls on snapchat and I found out by looking through his phone. Of course I was bothered by it but I know how addictions are and it wasn't an excuse for what happened but it hurt.

Here we are 2 years later. We have an amazing relationship where I feel valued and it is my first non abusive relationship as well. He goes to school in my same state just hours away so we don't spend as much time as we used to. I went to see him and everything was PERFECT. ... I looked through his phone. Again, snapchat but this time we got into a huge argument. I know he would never get physical with them but it hurts and I know we can get through this but I don't know how to feel. We have our problems and always manage to push through it, we have a healthy relationship. This is just one thing that I don't understand apart from that I don't believe he has left the person he was before to be committed to me.

I'm sorry it's so long. I need advice!!!