I am on Day 15 also. Days 12, 13 and 14 have been very difficult: no weight loss, headaches, lightheadedness, and HUNGER. I know you are supposed to stop when you get hungry but I persisted as I hope you will because today I feel much better, have little hunger and lost two pounds. I was ready to quit but now think I can go to 20 at least.
I also urge you to follow yogayak on youtube. He has done two fast trying both times to go to 40 days but stops in the 20s. I wake up to hid videos each morning comparing and contrasting our experiences. I find it very helpful and comforting unlike aaroncohen. Sushicatny, also on youtube can be interseting. She is very open and sincere.
Go day by day this id definitely not a straight line but hills and valleys.
What you are accomplishing takes tremendous will power ans a steely mind. Few could do it.