<human>: My [20M] exGF [F18] of over 2 years (the last year or so being long distance seeing as we go to different colleges) just broke up with me stating "I love you so much, but we're so young, and I would always doubt myself if I didn't explore my options while in college." She says she still sees a future for us but only after she "explores her doubts." (L.O.L. whatevs)

Anyways, in our conversations near the end, she said that it's likely she will sleep with someone soon in order to "answer her doubts." However, while I know in my head that's trivial and shouldn't matter, it's honestly what has tortured me the most (seeing as we've only slept with each other so far). Basically, every time I close my eyes or have a spare second for a random thought, my mind immediately jumps to images of her with other people. I can't stop. How do I stop this? I'm not asking to stop being generally sad, I know that's just going to come with time, but I can't go on torturing myself like this and I don't know what to do.

Can you condense the text into three sentences or less?
<bot>: I [20M] can't stop picturing my exGF [F18] with other people. It's relentless and I can't stop and I don't know what to do.