I asked my parents to purchase a badge for my account but when they made an account under my name they set the age to my mother's age.
Is it too late to change the age? Or can I still use the pass despite being under 18

As long as you're over 10 (the upper limit for child wrist bands) it should be okay. Just don't try to get into any over 18 or over 21 events (official or otherwise) and you should be fine. You'd probably have to email customer service to get your age changed but this close to the con it probably wouldn't be until after Aug 5th before they got around to changing it anyways.