Hi im 11 sorry! I have not gotten my period but i know a lot about them also period underwear:
https://www.google.com/aclk?sa=l&ai=DChcSEwiKpaOAv4CDAxV9xUwCHfdlBuoYABAmGgJ0bQ&gclid=EAIaIQobChMIiqWjgL-AgwMVfcVMAh33ZQbqEAAYAyAAEgIFcfD_BwE&sig=AOD64_1tA_Xw1eTr_4cq9_GpbdzSHimrEA&ved=2ahUKEwiLjp-Av4CDAxVph68BHeF2D4cQ0Qx6BAgOEAE&adurl=
And
https://www.google.com/url?q=https://www.ubykotex.co.nz/period-underwear&sa=U&ved=2ahUKEwiLjp-Av4CDAxVph68BHeF2D4cQFnoECAQQAg&usg=AOvVaw0N1dKTlNfjmUk-3Kg34qAl
I'm 10 but I didn't get my period yet..sorry. Also, I don't reccommend period underwear, pads are better.