I understand what you're saying and I sympathise. I've only just finished my GCSEs and I was under so much stress that for months I just cried all the time.
However, I was only under pressure from myself, because I wanted to get the best grades, and looking back now I realise that it's pressure like this that you don't need when you're trying to work hard.
You've obviously finished them now, but you may be doing A levels or similar in the future, and my advice to you is this:
Don't listen to what other people say, if you think you're doing enough then it's enough. If you think you're working your hardest then it's enough.
I know it must have been frustrating for your parents to act in that way, but it's best if you just look at it as their own way of looking out for you. They obviously care enough to make sure you do well, even if they went the wrong way about it.
Good luck in the future x