5yo DS regularly gets some sort of pain in his bum, keeps saying he can't "stretch his bum out". It was mildly funny to begin with but it's happened a few times over the weekend and he seems quite distressed by it :( Worst was Saturday where he was in tears and screaming, but he was also extremely tired, which we assumed was playing a big part of it.
All I can think is that it's some sort of cramp, or growing pains - are they real or invented by adults to stop kids whining about the slightest thing?