Sorry but I need to be honest here

You r so stupid. Bear that in mind, when you r a man/woman who is currently in a serious relationship, do not be too nice to other opposite gender. It's something u can think logically, if it's not you who think u gonna get lucky, lust then the opposite gender will or accidentally fall in love.

Don't beg for her to come back. You need to move on.
Improve urself to be more trustworthy. Even if she come back, she will always think you still gonna repeat the same mistake in the future. I know how girls think or else when you do hv a massive fight with her she will raise the issue again and again since it will be unforgettable mistake for her.

Sorry to hear that btw

Good luck then. Don't repeat the same mistake again or worse than that.

Let me tell you something, a good woman/man is very hard to find. But When u get urself one, keep since you cannot find elsewhere twice.