My DS(6) has recently started doing junior park run with his older sister. He's a big lad for his age, but we've always joked about his clumsiness and lack of coordination. However, watching him run I'm feeling a bit concerned- he seems to flail along, running almost sideways with his right side leading.
He's extremely slow- tries really hard but often comes last, and is overtaken by the 4 year olds.
I'm just a bit concerned that he's got something wrong with his gait- he seems fine walking normally but always insists on holding our hand in case he falls over. He also complains randomly about legs and feet hurting, but never anything we can really pin down, or for a sustained period of time. He's also started doing football after school, and is getting upset about never being picked because everyone thinks he's "rubbish". 
I showed a video to the GP who said it looked a bit unusual, but as he had no other symptoms and was otherwise fine, he was probably just uncoordinated. She also said that she couldn't think of where she'd refer him!
I know I'm a bit sensitive about him, as I had a medical issue when pregnant: was told he'd probably be a very low birthweight child and to prepare myself for possible cerebral palsy, developmental delay etc. When he was born at a whopping 5.5lbs(!), ate himself to the 90th percentile in 6 months, and hit all his milestones I think I stopped worrying. He's extremely bright and sociable- I'm just worrying that "something" got missed, and perhaps there is something I need to do. However, I'm at a loss where to start. We're in London, and have healthcare through my work, which might help if anyone can recommend anything.
Or just tell me to stop worrying. 