<human>: Condense the text into a few key points

Hello, i'll try to keep this simple and to the point.

I'm in a semi long distance relationship. We've both agreed we can see other people. But once we move to the same place together we'll become official.

Anyways, I hooked up with a girl randomly. I felt guilty after cause even though we agreed we could see other people I know she doesn't and we act like we're pretty much married.

After hooking up with this girl she found out I was in a long distance relationship and threatened to tell my girl and make it seem like we had something.

This caused me extreme stress and I wasn't sure what to do.

It eventually blew over but a few weeks later (now) the girl I hooked up with texts me telling me she's gonna talk to my girl about it. I eventually explained to her where me and my long distance girl are at and she understands and we're on good terms now.

So my question is, should I tell my long distance girlfriend what happened? I mean technically we agreed we could do this but I know she's going to be upset and it could cause some issues. The problem with not telling her is if she finds out eventually then it'll make me look bad for not saying anything and then she might not trust me cause I didn't tell her first.

I don't think she'll find out now but if she does it will be worse than me telling her now. 

What should I do? I hope this wasn't too confusing. This is causing me so much stress and anxiety right now. Hopefully someone can offer advice.
<bot>: Random hook up threatening to tell my long distance girlfriend we hooked up, but eventually decides she won't. Now should I tell my girlfriend myself or just let it go and hope she doesn't find out?