Itching and Thinning of hair. I do?

I had a reasonably thick hair 3 years ago.At some point my head started itching so much especially the middle part of the head.i used to comb my hair as soon as I reached home to see wheather if any lice were there.I combed so much but I didn't get any lice and I had no dandruff too.I didn't pay much attention to it for the first time but itching continued for several weeks or so  and it gradually stopped.I never faced itching after that time .One day i noticed that  i lost so much hair especially in middle and front part.now I can see my scalp .it is really depressing.what i remember is  that the hairloss and bald spots appeared after  the itching that happend earlier.i can see my scalp through my hair luckily there is no big bald spots .but I m really scared about losing my hair further.i lost so much of hair at  that time itself .what should I do??