First serious realtionship and break up

About two months ago my girlfriend broke up with me. We were together 2 years and actually we moved in together and were living together for 3 months. To me everything was great except for little problems here and there. One day she comes home and is acting very distant and i knew something was wrong. She admitted she had feelings for a co worker and that it was unfair to me of she didnt have total feelings for me. So within the next few days she packed everything and left. We talked a few times afterwards but then it was a couple weeks before we talked again. Recently she has been calling more to just talk and we have even seen each other a couple of times. She admitted it hasnt been the same and the fling with her co worker did not work out. I'm just wondering is there any way we could get back together or is this the end of it? she has cried on the phone to me saying she is not happy with work and how everything has worked out. I dont know what i should do. Any advice??

you were put on the back burner, now that things went upside down for her, she is coming to for comfort, you were not her first choice, sorry and you will always be her second or third. As bad as it may make you feel, you need to find someone that will not pack up and leave you.

Yep, she even told you her fling didn't work out. If you take her back, she'll do it again, and then come back again.

Its like a relationship pass to go out and screw someone else for a few weeks and come back.

Love her or not, she isn't worth the pain in the long run.

Once the relationship has end and if your ex moved on and be with someone else (Fling etc) then most likely you can't be with that person again because the relationship won't work..most likely you wouldn't able to trust her and you would feel insecure because you would always wonder if she will have another crush again and then leave you and have a fling with someone else.
She's just coming back to you and getting your attention because she is alone and lonely and she knows that you still loves her and want to be with her.
If she didn't have a fling with this guy then maybe this relationship might work again.

Ditto to what everyone else has said. You need to completely cut contact with her. Tell her not to call you for anything at all, and stop responding to her.

Actually it would just depend on you if you are willing to get back to her again. The consequences would be, for sure, you wouldn't have the trust you had before in your relationship and there would a percent chance that she will do it again to you.