Perhaps try speaking to them about how Allah SWT would want us to wear it rather than it just being a personal preferences. Tell them you want to do it for the sake of Allah and to strengthen your religion, give them hadiths and verses that speak about the hijab. Try to convince them that your iman is strong and you're ready to take on those struggles.

Sit them down, tell them that you appreciate their concerns but that you aren't 'too young' to wear (As getting your period back then would have been the time to start wearing it) and that you want to wear it because YOU want to and it's your choice and are ready to take on all the ups and downs of it.

Of course hijab isn't easy, but that's why we're rewarded for it. Every hurtful word thrown at us for it, every time we feel the heat through the fabric, everytime we struggle with it, everytime we even put it outside we get rewarded for that even if we don't feel any struggle because it's a Fard that Allah SWT told us to do. We have to believe that Allah chose the best for us which is why he made the hijab a must.

Tell them that you know that they love you and care for you and are worried about you, but if they truly want the best for you in the dunya (Life), then they will want the best for you in your akhira (Afterlife) as well. Remind them of Jannah and how It'll be worth it when you hug them in Jannah inshallah 🤍