<human>: Relationship rundown: Me and my gf have been best friends since we met, and started dating a little over a year after that. Been living together for 1.5 yrs now. Our relationship has been very happy, and we have had many adventures/travels together. I have never cheated on her, or attempted to, and vice versa. We have been monogamous from the get go, and have a healthy sexual relationship.

Last week I went to a concert with my best friend (a band we both love), afterwords we began a nonchalant conversation with a girl (let's call her Mary) in the lounge area upstairs. My friend had to go, and I continued to talk to Mary over the course of many hours. I felt a chemistry I have never felt with anyone. She connected with me on a level I don't think I've ever experienced, like we were completely on the same wavelength about our values, beliefs, thoughts, etc. 

She offered to take me on a walk (it was her neck of the woods, and I was unfamiliar with the area) we continued to talk and made it back to her place where we had sex. The most mind blowing sex I've had in my life. Anyways, we hung out a bit more and I went home.

I am very confused right now, I never believed in love at first sight, or that you could have chemistry bursting from the seams on all levels with someone right from the get go. I honestly feel like I found my soulmate (If you believe in that sort of thing) I love my girlfriend and she is my best friend, but I wronged her in a way that I don't think she could ever forgive me. Not to mention our families and lives are completely intertwined. What should I do?!

Can you give me the gist of the text in a nutshell?
<bot>: Been with live in gf for over 2 years, best friends for longer. Think I met my soulmate. How do I proceed?