sharp stomach pains

I am 20 years old and for a year now have been experiencing severe stomach pains, like someone is stabbing me with a sharp knife in the stomach area. It happens about once a month or once every 2 months, but when it does it puts me to my knees. I have been to the dr. and they ruled out gullblader, apendix, and they did blood work. I can not function when this flairs up. It last from 4 to 12 hours. It's like something I am eating is making it flare up and its the digestion periord that I go through this pain. Mostly happens in the middle of the night.  I can not pin point the food that is doing it. Maybe sugar? What could this be? And is there any medication I can take to relieve the pain.

[boron]

Where erxactly - which spot - do you feel the pain. On the side? Does it radiate to back, shoulder, or down to the groin? In what time after the last meal it usually happens?

Any tender spot on the stomach when the pain appears - I mean pressing on the spot aggravates the pain?