I do think women's pain is under-treated, IUD insertion no pain meds, no anesthesia, a lot of GYN procedures that really hurt are done with no help.
The worst pain I have ever felt, though, is still migraine. Not childbirth (I did those unmedicated) not broken bones, migraine is by far the most intense pain I have ever felt and that is not specific to women, though more common in women.
My tattoo artist said men complain, women don't. Not that it hurts us less, we just don't complain. Cultural thing maybe. My husband does complain when his back hurts; I just wait it out. Though if it persisted I'd be more likely to go to the doctor than him.
So maybe some of it is self-inflicted, we don't tell anyone we are hurting, but for God's sake, my gynecologist is a woman she should know that shit hurts!