Scalp and hair problems? please help?

im a 16 year old female and i have been having flaking on the top of my scalp for a while (the earliest i can remember was in 7th grade i came home from Knotts when my scalp got all itchy and ws intolerable). At the top, my hair is noticibly thin than the rest of my hair. At times if i dont wash it it tends to get really really itchy, for no reason and it can so untolerable. Now, it does not itch at all if i wash my hair every 2-3 days, its just really really flakey. Could this be the reason why Im loosing hair at the top of my scalp only????At first I though it was dandfruff, but i think its somesort of fungus that is causing it to itch and flake and appearently is causing me to loose and thin my hair. I was using a shapoo that has tar and helps relieve seborrheic dermatitis psoriasis and dandruff its called t+plus therapeutic shampoo from target, it did work but i stopped using it, and i started using it again, and does not work. My mom is trying to make me use selenium sulfide which was my brothers prescription but i dont think this will work, and this medicine has a side effect that causes hair loss, i already have that! i certainly do not want to make matters worse. I was begining to think i have demodex folliculorum but im not sure, i am going to the doctor soon but can anyone tell me what i could possibly have. or any suggestions on what i can use to treat my scalp. Please help, thank you.Scalp and hair problems? please help?
you need to go to the doctor and ask. this sounds like a serious problem and i wouldn't be trusting people on the internet to tell you what's wrong, they could just make up stuff!