I started having severe abdominal pain when I was 14 (I'm only 18 as well now) and was diagnosed with Crohns disease and now AS which are sort of related. Anyways it took literally 4 Internists to find the problem after countless X-rays, CT's, Barium study, capsule studies, colonoscopy, etc. Make sure your doctor runs a full blood panel, do an ANA test, and doesn't "guestimate" but rather does tests too. If I didn't have a colonoscopy I'd be a step behind. I understand the pain part though...it sucks and if you ever run out of options and need to take narcotics be careful with how you ask...doctors always want to cure things, not mask them which is good in theory but in practice its not always possible.
There are so many organs packed into our abdominal that its no wonder we have Internists having problems finding the issue. Maybe its your liver? Maybe it could be psychosomatic (don't shut that idea down, I considered it long and hard)?
C6 Herniation/Buldge (my docs debate), gen. nerve pain, ankylosing spondylitis, Crohns disease, Anxiety, Aspergers, and Mild Insomnia.
-Adderall 10mg am, Oxycodone 5-7.5mg 3-4x day,Lyrica 50mg 3x day, Klonopin 1mg night, Zoloft 200mg night. It could be worse :)