17, Hairloss, Premature greying,

As the heading suggests, the condition of my hair is very bad. I am 17, and greying of started around 4-5 years back. But it's become faster recently. Hair-loss wasn't prevalent even a couple of months ago but lately, I have started noticing considerable hair loss. I have also noticed small flakes fall down when I just shuffle my hair. I don't know if these are just dry scalp flakes or dandruff flakes. Also, my hair is frizzy and is not moisturised because i haven't applied oil for years. This might be a bit strange but when I was a kid, I had unknowingly applied soap on my hair for about two years before I stopped. When I consulted a dermatologist, he advised me to take hair supplement tablets and MOMETASONE FUROATE(0.1%). Hasn't helped much. My parents are asking me to apply oil on my hair. But how am I supposed to do this? And should I wash it off with shampoo after doing it? And will oil help in hair-loss AND greying? Or would applying oil make the condition worse? Please help me.