I spent my entire second trimester of my second pregnancy on 8-10 Percocet per day.
I was suffering from a muscle spasm in my back and hip (which I frequently get due to a back injury and subsequent surgeries resulting from my military service). My muscle spasms are no joke, they are basically a localized muscular seizure (or basically a big charlie horse) that doesn't ever relax and lasts for weeks. It's excruciating. I was crawling around my house very slowly because I could barely move and I'm one of those people that can pull my own stitches right out without cutting them and not bat an eyelash, so this pain is big time if it took me down that hard. The percocet really helped. It never went away completely, but the percocet did make it a LOT better. I still wasn't able to walk normally, but I was able to get around with crutches which I wasn't even able to do before percocet because I couldn't stand to be upright.
My OB at the time told me that the benefits outweighed the risks which were minor to begin with. She said the meds would make the baby drowsy too, but that didn't really matter since the baby was on automatic life support anyways. She said I wouldn't be able to take it when I was nursing because it would make him too drowsy to eat, but it was okay during pregnancy.
Oh and this was only back in 2007 so it wasn't that long ago. Anyways, I hope my story helped you in some way. Your OB has other options and he's just letting his own philosophy get in the way of telling you the truth. Maybe see if you can't find a new OB, or at least ask this one about something like Percocet.