Seems like this chick really nailed you

. It's OK, this happens often.
No matter how much you have going on and how successful you are, a women can drain you to the point where you feel you are nothing, but only if you allow her so! I don't know about this ex of yours, she probably loves you very much, you should think about that. Allowing a chick who just comes falling from the sky, screwing you like this, is not good. If you don't think to make up with your ex, I suggest you get out and sarge for other women. Your ex will probably not help you much. But, again, maybe you want to be with her again if she fits well for you. No matter what, never allow a women you don't know well to come under your skin so easily, it screws you up!
And believe me, when you are dating multiple women at the same time, then only you will have that feeling of having a lot going on. You feel better, more in control and women around you feel this too and for some weird reason have more respect for you. Don't appear as a player, however, this is not the best way to do it. This is called inner game (mindset, feeling, frame control, confidence a lots more).
Find some material for reading about inner and outer game and keep sarging a lot. And keep us informed.