Should I be worried? Ds seems fairly unfit

[Blossomhill]

Ds (8 in Jan) plays for a football team and dh watches him play every week. Ds only plays for 20 minutes (half a match) but towards the end always complains of a pain in his side, probably like a stitch. He also gets really tired wheras the rest of the team don't.
I feel a bit worried as ds has always got hot and sweathy easily as well.
Now he plays in the football team, goes to Beavers (soon scouts) and does swimming twice a week. He is tall but very slim build so no problems with his weight. He also eats a very healthy diet and we nearly always walk home from school (not to school as have to get dd to school).
Should I be worried? Is there anything else I could/should be doing? Thanks. He is my eldest so I do tend to worry about things like this.

anyone?

Maybe it is just a case of trying to build his stamina? I was a fit child but more of a sprinter than a long distance runner!
I could swim a couple of miles in a training session, but couldn't manage to run more than 400m before keeling over!

Why not get him checked over by your GP just to allay your fears? If he is breathless and getting tired easily, he could have mild asthma?

Other than that, perhaps he just needs more exercise?

I got diagnosed with "Exercise induced Asthma!" mind you. Dr thought that cold air (swimming was okay) and the exertion made me wheeze!

My son plays footie like yours and it's surprising to see how fitness and stamina varies from one player to another. The coach often substitutes the players to give them a rest. When the pitch is really muddy, its absolutely exhausting for the lads. My son is small and doesn't have the same muscle mass as some of the bigger players.
So long as your son seems healthy and is growing, I wouldn't worry. He probably needs to develop stamina and strenth in this particular sport.