Hey B.,
Girl, I know how you feel. My little boy was born in April, but as I got just about 7 1/2 to 8 months pregnant I had that same pain. It was from where his feet has gotten up under my rib cage. I would hurt under my ribs, all the way around my sides and into my back. I sit at a computer all day at work and some days I would just sit and cry as I did my work. I would get up and walk and stretch for a few mins and it would at least keep me from crying, but as soon as I sat back down, that awful pain would come back just as strong.
I remember it lasting like that for about 4 to 6 weeks. After the baby dropped, the pain let up quite a bit. It still hurt until I delivered him, but at least it was bearable then. The place his feet were under my ribs, the skin on my stomach is still numb. Apparently he was rubbing up against some nerves and eventually just killed some. From the pain you are having, I bet that's what your little guy is doing. I work at a Neurosurgeon's practice and I can tell you, something pressing on a nerve is some of the worst pain you can experience!
Keep you head up and pray for your baby to drop. It won't last too long. Congrats on the little boy! (Little boys are the greatest...I love mine like crazy!!)