Well, I don't have experience like yours myself when I was back studying in school. My daughters are so far still average and above average in their results. So I don't have the experience your parents have now either.
But the most important thing now is are you OK with what you have?
What is your plan or what is your next step? Because I am sure your parents will be less worried if you have sorted out what is your plan for your future and you can show them you have it figured out how you can support yourself in the future when you are grown up.
Not that your parents don't want to support you, but all parents will eventually grow old and leave us one day.
Even when you have a plan, parents will still be parents. They will still be worried and nagged. Because parents are parents... I know because I am a mom myself. And I can tell you even I am a mom now, my mom still nags me... So no matter how old we are, parents will always be worried.
So in the end, life is yours... You must take charge of your life yourself and think is this really what you want. Is this the best of you. Academic is not everything but it is the basic stepping stone into the real world out there. If we don't have the academic, we must find something else to replace it.
OK. That's it from me... Not gonna write anymore...