Your heart beats frantically in your chest as your stare down at your massively swollen tits. It should be impossible, but the evidence is right there in front of you, literally pinning you to your bed. Even as you look, they surge with further growth, making the bed underneath you begin to groan from the strain, and making you moan with a mix of pleasure and fear. Your arms are pinned to your side, covered by your breasts, and you let out a whimper as they surge with further growth.
How is this possible, and why is this happening? You hadn't done anything! Had you?? What could cause something like this? You'd never heard of such a thing! Yeah, you'd looked up cases about breasts growing before - there'd been several medical studies into breast hypertrophy and gigantomastia - girls before you had suffered from genetic disorders that had made their breasts continue to grow and grow. But it had been different for you! It had never made your breasts look deformed or anything. Even now, when they were literally beginning to fall to either side of the bed, they didn't look as though they'd been stretched out.
They were simply just...growing.
Your door slams open and your parents come rushing into the room.
"Jesus Christ!" your dad says.
"Honey?! What's happening?!" your mom shouts.
"I don't know!" you wail. "What's happening to me?!"
The bed lets out a sudden CRACK! And you let out a scream as it collapses underneath you, no longer able to hold the weight of your still growing breasts.
"We'll - we'll call someone!" her mom calls.
"Hurry!" you cry.
And then you let out a shrill scream as a sudden burst of growth shoots through you, causing your breasts to double in size in a single jiggling explosion, now so large that you realize you can feel the walls of the room to either side of you!