PLEASE 😭 Thin hair advice

Katie

I'm 20 years old, my hair shouldn't look like this. My hair has always been on the finer end of the spectrum, but it's becoming an overwhelming insecurity of mine.

My mum has PCOS, and I've always tested negative for indicators. Yet my hair looks like this (see pictures attached).

PLEASE, does anyone have any advice on growing thicker, healthier fuller hair? I hate so much as seeing pictures of myself because I know some part of my scalp will be showing. I have to tie it up and then carefully brush strands over my thinner spots just so I look like I have a full head of hair and it's crushing me