Hair is easy to pull out on the sides after a hair cut. Have no idea what this is

[OliverBrimmer]

So I am a diffuse thinner at age 19 and I've noticed that whenever I get a hair cut and cut my sides short, hair is very easy to pull out. But once my hair grows back longer on the sides, It is normal and not easy to pull out hair. I am panicking and I have no idea what this is. Lost and have no idea if I should start finasteride. My dad has thin hair on the sides but my grandfather on my mother's side has okay donor hair for his age.

Does anyone have any thoughts or has anyone ever experienced something like this? If so what is the position of your hair now?