Fluid buildup between my baby's scalp and skin

Hello everyone, I need some advise. I have a baby boy who barely turned 2 months this week. About a month ago I noticed that he had some fluid buildup between his scalp and skin. I took him to the emergency room right away they said this was normal and it would go away in a few weeks. When I took him to his pediatrician she was concerned because this type of buildup develops from birth and should have cleared up by now. I told her Im 100% sure he did not have this because its really noticeable and I would have definitely seen it. I had him via c-section but did struggle to have him naturally and pushed for over an hour. Anyhow she requested that I take him for some x-rays, but Im afraid of the radiation exposure at such a young age and that it will interfere with his brain development/function. Am I worrying too much?