Occasional Upper Abdominal Pain?

Recently, I have been getting pain in my upper abdominal area just below my rib cage on both sides. I think it hurts a little more on my right side. It only happens occasionally (I can recall it hapening about 5 times within a year?)... but this week, I've had it happen 3 times (2 times were really bad). I haven't been eating anything bad or really fatty this week and don't have any medical conditions that I am aware of. Could this be something to do with my gall bladder? The pain starts off not too bad and then gets worse for about an hour and then will stay constant for a while. It normally happens at night around dinner time but when I wake up, the pain is gone. I feel like I have to stick out my stomach when it happens because it hurts but when I am standing I have to use my arm to keep it in just under my ribs to stop the pain. When I sit, I keep my knees up to my chest to stop the pain. And it doesn't have anything to do with having to go to the washroom. Any ideas?