You dont know what you have ? Go to the doctor and get it checked out just to be safe.
About 10 years ago I woke up with a pain in my stomach, I thought I was just constipated, but after about an hour on the toilet with no result and the pain getting worse I was writhing on the floor in pain, and could not get comfortable in any position. I was taken to the hospital and they reckoned it was a kidney stone, gave me some drugs (dont know what) but they did help the pain. I was kept in overnight and made to drink lots of fluid (possibly just water, I dont remember). The following morning the stone was passed in to the bed pan and I was allowed to go home later that day. Thankfully it has never happened again.
They let me keep the stone, and I still have it, it's about the size of a grape pip (2mm dia). I couldnt believe something so small could cause so much pain.
Go and get it checked out.
Good luck !