Do I have a thyroid condition?

So, my older sister has a thyroid condition (hypothyroidism), and sinse it is genetic, I was recently tested for it, and I didn’t have it.

I did some research on the disease and I have almost all of the symptoms of it! (ex: light periods, hair falling out, get cold easily, constipation, really thin and flimsy finger nails)

oh and I’m a 15 year old girl

even though my blood work showed negative, is there a chance I could still have this disease? what should I do, should I get tested again?