There's a number one trick to cheating: don't get caught. As long as you never get caught, you never have to confront those ugly feelings or all the pain you're inflicting on your partner. And this may be blatantly obvious, but the key to not getting caught is to not be in the same place as your partner while you're cheating on them.
If she's started tracking your movements all of a sudden, then this could be the reason why. Is she suddenly extremely interested in where you're going to be during the day, at what time, and for how long? Well, it's not because she finds your activities fascinating, or even that she suspects that you're cheating on her. The most likely explanation is that she's trying to make sure you're not around to catch her.