I'm a 17 year old girl. And about 2 days I took a poop and my tailbone has been hurting when I lay on my back ever since. I also noticed that my tailbone sticks out a little now and I can feel it This has never happened to me before. I didn't injury myself or fall on my bottom or anything. I was wondering if this is normal or should I go see my doctor.

I doubt it's actual bone that you feel, so yes, see a doctor, in case it's something like a herniation. And while waiting for the visit, have your mother or other older person look to see what they can see, and feel it, to describe to the doctor's office when they ask what you need to be seen for.