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

I've been together with my ex-girlfriend for seven years and she broke up with me about 4 months ago. I did about 2 months of no contact and we only chatted a bit via facebook. 
However, last weekend we bumped into each other at a party and we ended up at her place and had a really fun night. We immediately connected again and even though we haven't talked about getting back together it is pretty obvious that we both have strong feelings and missed each other after the break-up.

Yesterday when we met again she told me that she felt really guilty and "confessed" that she hooked up with another guy a few weeks after she broke up with me. She told me that it wasn't very emotional, that it wasn't good and that she regrets doing it since to her it somehow felt like cheating on me. 
She wanted to know whether I had met someone else after the breakup and I told her that I had sex with another woman and added that it also didn't mean anything, that it felt bad because I still had feelings for her etc. (which is the truth). 

After I told her she cried and I was still shocked that she hooked up with another guy. I feel like I shouldn't really care about it because after all I met another woman as well and we weren't together anymore - she broke up with me and we didn't cheat on each other. The first few hours after she told me about it were like a nightmare to me. And I still can't stop visualising how she kisses another guy and has sex with him etc. For whatever reason I feel like crying because it seems as if I can't handle it and nothing will ever be the same again because this line has been crossed. I'm completely devastated even though I feel like I'm being completely irrational.

How can I handle this and deal with it? I really still have strong feelings for her but now it seems that whatever relationship we are gonna have, it will always be tainted by this.
<bot>: Met my ex-girlfriend 4 months after break-up. We still have strong feelings for each other but I feel devastated because she had sex with another person during our break-up and I don't know how to deal with this.