The reason that childbirth is so painful is due to the contraction of your muscles and uterus during the labor.
Also when you're actually giving birth you're pushing a large baby out of your tiny hole and the babies head is stretching that hole to allow it to go through it.
The babies head changes shape and can shrink some while it's going through your birth canal but anything larger than your birth canal that is going through it is gonna cause some intense pain.
When you're going through that pain of childbirth you might think that you'll never want to go through that again or wish you hadn't gotten pregnant.
But for most people who hold their child the first time they will gladly go through it again and are glad they went through it the first time.
I wish the childbirth wasn't painful but it is and it's not as scary as I thought it would be.