I think there are a couple of ways to go on this - but ignoring it isn't the one I would choose either! As another mom said, you know your child, and you have 4 others so you know when one is extremely uncomfortable and in pain, rather than just a little fussy. So you should definitely insist on a better response from the pedi - that can be a new pedi or a referral to a Gi specialist. However, you should prepare yourself for the likelihood that there will be prescriptions for drugs and possibly some tests. Other moms have posted on this site that they don't want their little ones to have tubes and scopes.
Then there's the whole elimination diet theory - lots of moms start casting off everything that could possibly trigger this problem - dairy, soy, wheat, and so on. Sometimes you relieve the problem, but then you have to decide when and what to put back into the diet. If you do this, just put one item back in per week to see if it's a trigger. Once you identify the problem, then you have to decide if your child can never eat it again, or if it's something about that particular brand. For example, sometimes people eliminate soy, but is soy the real problem, or is it because it's a soy product treated with something else (e.g. alcohol wash) or with some other irritant or contaminant in it? This can be a huge hassle and not always fruitful, especially when you have other children to keep track of. It's hard enough to get them all to eat a healthy variety, isn't it?
Other solutions include comfort measures like elevating the head end of the crib (either the whole crib or just the mattress), doing things to move the gas around, and so on. You could also try to balance out your child's system with a nutritional supplement but you have to be sure you have a top product with no contaminants and top quality ingredients. That is very hard. There have even been some articles recently about most supplements being more trouble than they are worth. I can help you in this regard if you want more info because I have so many friends whose children got rid of supposed food allergies and stomach issues. I can recommend a product but I don't want to push it on you if you want to go the medical route.
Good luck to you - definitely don't feel pushed by the doctor to ignore this though! Trust yourself!