How can I water fast safely this time?? Please help??

I'm 15 years old, and this is my second attempt at a water fast. I only started today so obviously no symptoms are showing. My last attempt was about a month ago; it didn't go well. On the third night I tried walking to my kitchen for more water, and I got there easily. but the way back- I lost my vision- everything was black. I remember my back hurting so bad all the sudden I didn't think I could walk- All I remember is whispering "so much pain so much pain help" I barely made it to my room- I fell onto my bed and dropped the water bottle. I don't remember if I went to sleep after that or passed out. But it was pretty traumatic. I am not happy with my weight and due to a thyroid problem its VERY hard for me to lose it by "eating right and exercise" This is pretty much my only option at this point. How can I do this fast successfully, without dying, or having a traumatic experience. Tweet