Heh...
You really need to be working on your social anxiety issues and fixing yourself. Not dating, not worrying about who she's dating. Be happy that you dodged a bullet by not asking you to marry her. Take time for yourself, and understand that when you're that involved with someone that you need time to grieve for the loss of a relationship. Sure, the person isn't dead, but the relationship is, and having to see reminders of it daily certainly doesn't always help.
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."