<human>: Can you condense the text into three sentences or less?

I (19m) have been cheated on in two of the three relationships I've ever had. The last girl I was dating told me a few months ago that she had been cheating on me, and I didn't know how to react at first. We tried to work our relationship out. She seemed ashamed of it, and acted like she still wanted to be together. I stupidly bought into it, and we worked things out for about another month. We broke up, and the next day, went out and had a fling with the same guy she cheated on me with, and shortly after is now seeing another guy. I know it's all stupid, and I really shouldn't care, but I've been really down lately. My relationship with my parents haven't been that great since middle school, I'm in my first year of college, facing academic probation because of my GPA, and my friends only really seem to talk to me when they have some sort of problem with their life. Throw the whole cheating situation in, and... I just don't know what to do. It makes me wonder if something is wrong with me? I don't know.
<bot>: have been cheated on twice, situation added to stress, feeling really down, could use advice, or even just a good smile.