Can dogs detect pregnancy before even you know?

Melissa • 25 and pregnant with our first little Peanut!
So I was at my parents tonight and I was down on their floor petting their two dogs, and the both of them acted strangely toward me. One of them sniffed my legs and butt up and down and I was sitting cross legged on the floor and she attempted to dig in between my legs and was sniffing me like crazy. They're both pretty attentive dogs but that was a little unusual. I'm technically a few days before AF. But my cycle has been crazy these last few months. 
​Has anyone else had their pet figure it out before them? Or am I overreacting?