Facebook shortcuts?

Question

Facebook shortcuts? Hello, I am f/26 and my boyfriend is m/24. We have been together almost a year now. When we first got together, I caught him texting a girl he was into before me. He said he "didn't think I was that serious about him", and that he was sorry and took her off his phone right away. We haven't had a problem like that since. Flash forward to this week, our one year is tomorrow. Throughout this week, he's been sort of distant, coming home irritated and wanting to go right to laying down in bed or getting drunk. I thought he's probably exhausted from work, we don't get much sleep anyways, but I still had a bad gut feeling. Yesterday I was helping him do something on his Facebook and there was a girl's profile in his "Facebook shortcuts". When I asked him, he acted like it was no big deal, denying ever looking at her profile. Then he told me they used to be neighbors. Then he admitted he used to check her out before me, but she "got unattractive after having kids".. He kept saying he swears he doesn't remember looking at her profile, saying he "has a beautiful girlfriend now, so why would he check out someone else". Crying saying he's sorry. Begging me to stay. He deleted and blocked her right away. We've both been cheated on, it's always been a thing of his to "be loyal", so what do you think really happened? Is he possibly tired of me? Is he maybe losing interest in how I look? Or did he really click her profile on accident? I can't seem to figure it out.