Male Baldness Info

I started using Head & Shoulders shampoo last year. After a few months on H&S I noticed a small bald spot I had on the top of my head towards the back seemed a little larger, but dismissed it for just being the way the hair was pushed. However, lately when I switched to a new Head & Shoulders formula, my hair started rapidly thinning to the point where theres a line of almost baldness with the hair going in either direction the way it grows on the crown of my head.
After some research online, it seems like others are reporting this issue as well including teenagers and its all occurring on the same part of the head.
I’m 21 with thick hair and absolutely no Male Pattern Baldness in the family. The fact that this is happening so rapidly has left me wondering whether or not it actually is MPB or if it’s a reaction to the shampoo that only a small number of people get.
Information on this issue would be greatly appreciated. Thank you.