I saw my boyfriend speaking to his ex girlfriend at the store. The way she looked at him made me so mad. 
Oh man, I would have been really frustrated. Does she know he is dating you now?
Of course, our town is so small. However, I could be letting my imagination get in the way. Gosh, her smirk is what made it worse.
It's never fun to see your significant other around someone they used to date. At least he is with you now and I'm sure you have nothing to worry about!