Insanity- round 2 last week

Hi all!

So there you have it, ive lost my workout mojo!
My body is exhausted i could not even finish the max plyo yesterday, quit half way. My knees are hurting and i am just plain exhausted. I went back to work two weeks ago and this is where the exhaustion started and my willingness to work out. I come home from work and deal with the kids until they go to bed, have to make dinner, lunches etc... No energy to excersise after. Just want to plop on the sofa and sleep.
I want to take a week off but i feel bad about it. Not sure if anyone can offer any advice or words of wisdom. I want to wake up in the morning but excersing for an hour and getting the kids ready for school / daycare scares me. Should i get a pre workout energy drink???