Well, I had a hernia in a different location than the location you describe as a child... and I don't really remember if it hurt all the time, but would suspect it would hurt more if one was causing a strain on it.
I have also had costochondritis that we thought might have been a gallbladder of liver problem due to location on the right... it can be very painful and usually, a practiced doctor can pinpoint a painful spot when pressed with it.
But may I suggest you try to make a same day appointment with your family physician (who has seen when the lump is not out what the area looks like) when the lump is out- kind of like going in with a car when it is making the noise you want diagnosed? If you try coughing and holding the area, can you feel it bulge out?
Has the GI doctor said there were any sharp bowel loops in that area above the belly button? Did he include an abdominal ultrasound or MRI/MRA in his testing?
Im caucasian and I smoke. My gasterologist dr has ran many tests because of pain on right side and under ribs. But no luck on diagnosing. They have never commented on lump in belly. Would a hernia hurt all the time? Because this pain comes and goes. When I get it, it can last for days.
I wonder if you may have an abdominal aortic aneurysm. Do you have any of the risk factors for this (see you are not male and not 60 or older)- but, are you caucasian, do you use tobacco products, do you have high blood pressure, do you have a family history of aortic aneurysms or have you been diagnosed with atherosclerosis?
Do you think you may have a hernia? Have you maybe done some heavy lifting or something that may have caused a tear in the abdominal wall muscles? With the pain under your ribs- on the left side toward the middle is your gallbladder, and to the right of that, your liver. On the right side, the stomach is in the front and behind that the pancreas....have you asked your doctor if an abdominal ultrasound might be in order?