Mine are as well. Found this out, quite by accident, years ago. My wife and I were naked in bed and 69ing, when I slid down to pay attention to her large breasts, giving equal time to both. I was getting into it and feeling a little devilish to boot, sucking harder and biting them as well, when my wife said ouch, that hurts. When I said yeah, yeah, yeah, deal with it, to which she replied, oh yeah, lets see how you like it, and proceeded to suck and bite mine as they were inches from her lips. She did and was the first to feel my member stabbing her in the stomach.
Well well well, looks like someone likes it. I protested and she sucked and bit harder, getting an "ouch that hurts," from me. Then she sat up and turned me over her knee for a spanking. "Ouch, honey that hurts!"
"Deal with it," as she spanked harder.
When she finished, she put me on my back on the bed and told me to pay homage to her naked bottom with kissing, sucking and biting and to thank her for finding another hot spot on my body and for my correction in treating a lady like a lady.
Sometimes when we're out in public, beach, party, restaurant, she'll give me a quick bite and suck (when nobody's looking, to get a rise out of me, and sit back and watch my embarrassment), when we get home or to our hotel room will release the pressure.