Although my labors were most certainly not pain-free, they WERE quick, and I HAVE had dental procedures and headaches that were more painful.
That said, I suck at being pregnant, and have in all my pregnancies considered terminating due to the sheer amount of suffering I faced in the early parts. (They sucked the whole time, but the first tri was always the hardest.) I felt very guilty and yes, sometimes thought the babies could sense that their mom wasn't wholly perfect, glowing, "omg I am so happpppppy I am pregnant, this is a miracle!!!!". This even with my planned and much-wanted pregnancies. We're all put under a lot of pressure to be pregnant/birthing goddesses with nary a negative thought, and if we're not happy rosy sunshiney the whole way through, we're at fault, we're bad people, the babies judge us, the whole nine.
Incidentally, we all have different reactions to the not-everyday experience of labor. My first was pretty quick laboring but pushing was very difficult. When it was done, they gave me the baby, and I could care less. I didn't even look at him. I know you're "supposed" to look down and see your baby and go coo and aww over it, and fall in love and start saying things like "oh i love you my little baby" and kiss kiss and count the toes. I felt like I was high from the labor hormones and I totally didn't care there was a baby there. I was grinning and making small talk with the nurses. They wrapped him up and gave him to me again and AGAIN I ignored him, so they put him away. Later on, like an hour or two later, they were wheeling me to another room and put the baby in my lap to hold, and I held him like, wtf is this thing, and I was kind of weirded out by it. Then they left us alone in another room to recover and yes, we did eventually bond, but it took a few hours. I'm no less bonded with him than I was with my daughter, but it definitely wasn't the picture perfect documentary birth. You know what? We got it over it. ;)
Incidentally, I'm pregnant again, and have zero, zip, zilch bondy feelings with this baby. I feel sick, not preggers. I don't feel happy, I don't rub my belly, I don't, well, anything. And yeah, we tried for a year to get pregnant, and this is my last pregnancy, so I "should" be feeling over the moon that I'm knocked up. Meh. I'm being gentle with myself. I'm sure the bonding will come, eventually...