Been there, done that! ...and Im 26.
Just about a month ago I woke up with some nasty back pain. Thought I just slept wrong or something. Soon enough I was doubled over on the floor. Drove myself straight to the ER, which thank god was only 5 minutes, but seemed like forever. It was bad enough that I left the house without my glasses, and didnt realize it till I started driving. It was the second time Ive had that kind of pain. The first time I had some really good pain meds left from a tooth extraction, which saved me the trip to the ER. I wasnt so lucky the second time.
They did a blood workup, all sorts of tests, and xrays. They figure I passed it in between tests.
Its kinda hard to explain, but I figured something was up. Generally, if you are prone to stones, and you notice any changes in how you "go", you better see a doctor.
My whole family has had them with exception of the oldest sister. My dad drove himself to the ER a few months ago, which was a 30 minute ride for him. I can only imagine what that felt like.
Like was said before, kidney stones are made because there are certain things in your diet that help to make them. Which, is why they will want to catch the thing when you do pass it. They will want to analyze it to see what its made of. You will end up having to go through a strainer, and possibly keep a urine sample for them to test.
All I can say is good luck. Drink lots of water, avoid the soda, and keep some pain meds close by.