My golden puppy keeps biting my hands — is this normal or do I have a problem dog?

Okay so i've had Biscuit for about 3 weeks now. She's 4 months old and absolutely the sweetest thing — but her teeth are WEAPONS. Every single time i try to pet her or play with her she just goes for my hands. Not aggressive or growly or anything, she's wagging her tail the whole time, but it HURTS.

I've tried yelping like i read online, i've tried saying "no", i've tried redirecting with a toy. None of it seems to be working. She actually gets more excited when i yelp lol. My hands look like i got in a fight with a cactus at this point.

I don't want to be dramatic but i also don't want to let bad habits form. Is this just normal puppy stuff that'll pass, or do i need to be doing something specific? She starts puppy class next week but i don't know if i can survive till then.