I don't have any experience with this specific concern, but I just want to mention that any time you notice something that creates concern in you, it doesn't hurt to put yourself at ease by checking in with the pediatrician. You don't necessarily need an apt for questions - or should anyways. My ped is great about phone consultation. Moms notice tiny details and have a good sense about possible problems - just call your ped. Mine has hours in the am for ?? but they will take them anytime if something comes up later in the day. Just tell the receptionist that you have a concern/question for a nurse/doctor. They will take a brief message and your child's name. They pull the chart and someone returns your call. It has always been the most helpful thing for me to settle my wild thoughts about what might be the problem. If the nurse/doctor feels it's necessary to see the child, they will tell you to make an apt. If not, they can offer suggestions for behaviors that might be of concern and instruct you when it might be necessary to make an apt.
Another option is to try chiropractic care. A ped isn't likely to refer you, but insurance doesn't usually cover infants anyways. The chiropractor usually has a low fee for children because of this. My children have been going since they were a few days old. Any time they are sick, we take them for an immune boost. We also know they need to go when they develop big attitudes - it's their way to say they are uncomfortable. Many issues that may be handled with surgery or braces can be easily and less intrusively managed and repaired with chiropractic care.