More than half Hair lost in last decade.

I am a 26 year old girl currently working in the private sector with a busy and considerably poor lifestyle. I have normal appetite but usually lack sleep quite often. Initially I had extremely thick hair, so much that it didn't fit into my fist. Now, over the last 10 years, I have lost more than half my volume... Length-wise hair growth is fast actually but volume does not seem to come back. Hair falls but doesn't grow back. Also I have itchy scalp which is why I require to wash my hair thrice a week. Whenever I scratch my scalp too hard, much hair falls off. My hair seems to be an oily scalp and dry hair combination. This seems very alarming as I am left with less than half of my hair volume and bald patches here and there are evidently noticeable. My question is, is this repairable? Can I have my original hair volume back? Is it too much to expect?