Every single day I feel fatigued... why?

Everday no matter how much coffe I drink, usually 2 cups, 5 hr. Energy etc... I feel so tired. Sometimes light headed and dizzy too. I'm not pregnant. I am a stay home mom. I have 1 child and cannot seem to even clean anymore. I have no energy and the dr.s don't get it either. Could I be really sick? I'm worried I have an illness. Please help.