So... I dealt with those stabbing pains too. At first, my back was killing me so badly I honestly thought it was my kidneys. Went in for an ultrasound, and they told me my kidneys were perfectly fine. Looking back, I connected the dots later—I had stopped taking birth control after a year, and these pains flared up just a few days after I quit. It’s the exact same sensation you're describing: that sharp, stabbing, dull ache, mostly on the right side, though sometimes the left. I actually feared it might be appendicitis, but I don't have any other symptoms. I've got an ultrasound scheduled now, just waiting for my period so I can finally go. About three years ago, I actually ended up in the ER because of intense, stabbing pains—way worse than this. They suspected appendicitis and kept sending me back to the emergency room every single day because they couldn't decide if it was actually my appendix or not. Then, after about five days, the pain just vanished completely. Like nothing ever happened. In the end, they didn't even give me a straight answer...
Anyway, I wondered if this could be happening because I stopped those pills; maybe since my ovaries are trying to function on their own again, things are a bit more difficult, hence the pain. I don't know. My first period after stopping the pill was two weeks late and absolutely brutal.
It's not like I'm in constant pain or obsessing over it, but it's definitely bothersome... more annoying than painful, really.