You are not using proper form, or the floor is simply too hard.
Use more padding and tilt your hips in towards your belly button.
Sit-ups are hard to do perfectly correct, and may end in more harm. Other alternatives for ab-workouts would be better, like crunches.
same thing is happening to me, my mom is taking me to see a specialist.
The tailbone is the end of the spine.
The coccyx is what we refer to as the tailbone.
Tailbone.
The coxxyx is the tailbone
He didn't do situps, silly!
The medical term meaning pertaining to the tailbone is coccygeal. The proper name for the tailbone is coccyx.
Coccyx
50+ sit-ups a day for 2-3 weeks (your muscels might hurt the next day,but that's actually a good thing!!)
the cocyx is the tailbone
coccyx
Coccyx