Napping= Insomnia.. anyone?

By 9 - 10 am I am already drained and so tired I feel sick. I sometimes will HAVE to nap when I put my 2 year old down to nap.. and let my other three children know what I'm going to do if they need me. . I sleep for even a half hour or hour and I am not able to sleep until 3 am! If I don't take the nap everyone pays for it. If I do.. everyone pays for it and I am more tired the next day..