Somethings up, and it's not my heart rate...

I've felt strange all dang day. My heart rate has been really slow. I could attribute it to low blood sugar, but I've been eating so maybe not. All I know is I tried to hit it hard and do 2 back to back workouts tonight at the studio. I couldn't get my heart rate up. I don't know if it is because I was tired so I couldn't push or what. So I will accept that today wasn't the best. I will go to sleep and get up at 4:45 and try again. No use beating myself up.