<human>: Provide a brief overview of the text.

We were casual acquaintances for several in my sophomore year of high school, his junior, before we started dating over the summer. It was my first relationship, I hadn't even gone on a date or kissed anybody before. He knew this and was very reassuring. Everything about the relationship seemed perfect at the time.

A little background on me: I've known for a long time that I probably have an undiagnosed anxiety/paranoia disorder. Basically I'm not particularly trusting of others. But I made a vow to myself that I would try to be a normal teenager and just go with whatever life threw at me while I could. So I dismissed any doubts I had as my normal overthinking/paranoia.

One night, the fall after we started dating, I get a text from his phone number. He told me he was hanging out with friends that night, so I thought it was a joke at first. The text said something along the lines of "I'm _____'s girlfriend, who are you? Sorry this must be a little shocking." Turns out it was completely true. He was dating this other girl on and off for about two years when he started dating me. She didn't have any clue about me either. 

I broke up with my bf over text that night. Him cheating immediately invalidated every part of our relationship in my mind. We didn't see each other for a few months, but it was in a work environment and we didn't speak to each other. I haven't seen him since, almost a year and a half ago now.

I haven't had a relationship since, either. It took me almost a year to even think about dating again, but I'm still terrified to throw caution to the wind and let anyone be that close to me again. Getting cheated on only served to make me more wary of others. I'm going to college, and I want advice on how to get past this mental block.
<bot>: My first bf cheated on me for the entirety of our relationship, now I can't get rid of my trust issues.