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

I posted this in another forum but I'm actually struggling more than I thought I would with this. 

Ex of 4 years left me a year ago and looking back it was the right call. I originally ended things as the trust was gone due to her lying and talking with ex and one night stands behind my back. I tried to make it work and she pulled the plug.

Long story short it's been a year and I've for the most part moved on. Within a few months she had already been with multiple guys. She tried coming back after those guys didn't work out and I shot her down. She has never stopped contacting me though since the breakup. 

And here I am, dating someone new for three months and things are going well. Knock on the door and it's her, telling me she still loves me and can't imagine not having me in her life. Shot it down again very cordially and nicely. Didn't bite her head off. I assumed I would be OK but I can't stop thinking about it. Don't really have anyone to talk to but I thought she was the one. When she ended it and moved on it hurt like hell but it have me the motivation to move on as well.
<bot>: ex left me and moved on fast, found out grass wasn't greener. Maintained a distance of contact and had finally broken down and asked for me back. Shot it down and feel like crap.