G-tube for 15 year old with CP... good idea?

i am not on any curves on a pediatric growth chart. i am 3rd percentile on everything. i am starting to have problems drinking a specialized nutrition formula and having severe problems with solid food, i cant eat much at all. after i eat just a little i feel "full" i definatly dont enjoy eating and my enjoyment for drinking is diminishing. my weight is at 101 and dropping very slowly. there was a crash in last december to this january before i got on the formula dropped 4 pounds in december from 105 down to 101 dropped another 4 in january down to 97. it was very scary and i still havent recovered fully, i have quadriplegic spasticity and also i have noticed that eating is getting very hard because my gag reflex keeps triggering. the doctors are saying "no its not nessisary" and i stepped on a perfectly calibrated scale and its showing 93 pounds, 4 pounds less than what it was in january, anything below 90 is considered critical, are they going to wait for it to go critical.