<human>: Can you summarize the given text in a few sentences?

The breakup came Sunday night, a week before our 1 year anniversary, which I was quite excited to come up for and had many plans for her. We were doing the distance thing, but it was going great! We managed to see each other every 1-2 weekends and always had a great time. We also talked quite openly about our future after we would finish school at the end of this year. Then she dropped this on me quite suddenly and gave a multitude of vague reasons (wants to stay in her city for work after school but didn't discuss it with me, not me it's her, didn't have as good of a connection as we thought, distance was getting too hard, thought the future plans sounded good at the time but got scared). Some of these reasons are completely understandable yet I felt like there was still something she wasn't telling me. I asked her if she met someone else and she denied it and got upset when I asked a second time.

So we get to the part about her Facebook. Yeah I'm a sneaky bastard but I logged in to find her talking to her friends about a guy she met on a class outing two weekends ago. Turns out this weekend they did some drunk making out and slept in the same bed (no sex) Friday and Saturday night. Then she dumped me Sunday night and had sex with him the last three nights.

What do I even do here? We left on a good note and I haven't contacted her in a couple days, but I'm upset she lied. I also realize I'm at fault for logging into Facebook. Do I approach it? What do I do to make myself stop checking her Facebook routinely?
<bot>: Found out through hacking my girlfriend's Facebook that she cheated on me but wouldn't mention it when giving reasons for the breakup.