Worried about booking a doctors appointment?

i was thinking about booking an appointment today for the doctors about my hair, like its not growing as strong as it used to and i parts of the hair looks really thin and some parts you can see not much hair at all, i'm only 19 and not sure what caused it, cos i have had dandruff, and also pulled my hair a lot with gel, could this have caused it and how would doctors help? Just worried cos if they do operation or something. Thanks