Probably not if it's that extreme, but if you see an old ex with someone else and feel a twinge of discomfort, I think that's normal. Especially if you've had an actual romantic and sexual relationship with the person. It's a little weird/awkward.
No. If you were completely over someone, you wouldn't care at all. I used to have a crush on this girl back in middle school, and at this point in time, I couldn't care less who ends up with her. I'm completely apathetic.