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

So about six months ago, I met a very attractive guy online through my university's study abroad forum (our universities are partners and we were going on exchange to each other's schools). We started chatting, quickly hit it off, skyped occasionally, and texted constantly. It was very casual and we never met in person, but we did sext quite a bit.

 However, he would not accept my Facebook or Instagram requests and something felt a little fishy. After a bit of snooping, I figured out that he has a girlfriend. I was feeling pretty humiliated and upset, so I took a couple hours to think it over. After collecting myself, I told him that I had found out about his girlfriend and that I was not comfortable continuing our relationship. I cut off contact, but I still feel quite guilty about the whole situation. I never bothered to delete the kik messages and still have them on my phone. Am I responsible for telling his girlfriend or am I off the hook on this one?
<bot>: Found out a guy I was casually sexting with for months has a girlfriend. It is my responsibility to contact her or can I just let this go?