<human>: Can you give me the gist of the text in a nutshell?

Last few days have been high tension have been high tension between me and her. And I'm scared as fuck she will leave me. 
Started with her being told that I've said to some people the stuff we do behind closed doors leading on to something about drunk me and cheating, (which I have never done) :(. we met up today and had a great time with each other but it ended badly cause she found out about me and another girl talking about being together (turned out to be her sister) three months into our releshonship. I don't know why I even considerd that fuuuuuckkkkkk the only reason a yes to her even came into my head was cause I tried and failed 3 times :/. We argued about it and I thing I messaged her last night (convo with another girl about why I won't cheat on my girl with her. gf took it the wrong way) and I know I'm only last chance with her. She amazing girl the first girl I ever properly loved and I form think I will ever stop loving her. Everything here is my fault and I don't know what to do. Help
<bot>: ! : On last straw with girlfriend because I did me to many stupid things regarding us and I was stupid with another girl (nothing happend though) and my other idea backfired.