3rd flush & still no stones

i've tried the flush 3 times now and absolutely nothing has happened. I don't feel any different and haven't seen anything that would resemble a stone. Could it be that i simply don't have em? I've done the flushes by the book (used moritz recipe) so they should be working out. Please, tell me every bit of info as to why this might not be working and i'll figure out if there's something i've missed. Fatigue is the number one reason i'm doing this but i also have other issues that i thought might be related to stones & diet. Anyways, some help would be much appreciated!