Pain after birth?

I'm currently 2 1/2 weeks post partum. I delivered my daughter vaginally, and only had alight tearing.
Over the last week or so, I've had some slight pain in my lower right abdomen. It's been intermittent, and when I called the nurse at the OB's office, she didn't seem concerned. 
Last night, the pain got a little worse. I don't feel it when I lay down, and slight to none when I sit. It's mostly when I stand up or walk that I feel it. I don't think it's my appendix, but I'm wondering if maybe the uterus still hasn't healed? Everything I've read online suggests uterus pain goes away by this point, so I'm starting to worry.
Anyone on the same boat that can shed some light? I'm calling the Dr's office today when they open but just curious.