Im so tired!! Insanity to blame?!?!? please help

I started insanity last Monday Aug 4th and ever since i have been so tired!! I dont do anything all day, i am a bank teller. So i sit most of the day and then i do my workout after work. Is there something i am doing to make me so tired? If you have done insanity and had this problem please help!! I like this program bc i am already seeing results and i dont want to stop.