Weird...

My period was supposed to start yesterday or today...days sometimes vary. Wednesday I wore a pad all day because I felt like I was going to start. When I got home, I noticed a few drops of brown blood on the pad. Yesterday and today I've had nothing else. Took two first response hpts yesterday...both very negative. My breasts are hurting off and on and I've been exhausted yesterday and today. When I ate lunch, I felt nauseous afterward. Is it possible it was IB Wednesday and I didn't wait long enough to test???