One time when my BF and I were driving home on the interstate, we had a car following us and pretty much tail gating us. Unlike you, I am a paranoid person! Lol. I thought it was some crazy guy who was trying to get us to race him, but it turned out to be an undercover cop trying to get us to speed up. It could be that, and maybe the cop was just irritated that you were patient so he decided to follow you! Lol... Cops get mighty angry when they can't write tickets. At least here they do.

If that were the case, I'm sure you would have noticed something in the back seats though.