hair hair hair ...

i need help this is my first ever post
.. my going through the worst hair fall ever .. i used to have shoulder lenght long thick hair .. ALL of a sudden they strted fallling so muchh …
since last 5 years ive been straightening them but they havent fell to such an extreme .. is this because of the straightning ??
i do take multi vitamins and had my blood test which says tht nuthin is wrong … dr’s nvr hav a satisfactory answerplease tell me what shud i do? ive nt been using heating products since last 8 months nw but stiilll nuthing worked … please tell me somthin tht really work …
why do people say that shavin off the head makes hair grow thick ??? is this true or just a myth?
waise b i wear a scarf … n if this really works am ready to do anything to get thick hairs …
n girls out thr who hv thick long n beautifull hairs please take care of them n dnt ruin them by using any kind of heating products … n pls help me out .. loads of dua’s