Dear HappyPad
A couple of explanations come to mind from what I have just read.
The mechanism for your current injury is a kick of a ball in the air (unsure which foot though) with sudden pain in the calf muscles. Also similar pain in the other leg but not as severe...
This pain felt better as you walked home but tender when you touched it...
It could be:
Recurrent Calf tears...there are two (or three if you want to be technical and consider the two heads of the gastroc) muscles in your calf area...the Gastrocnemius and Soleus...sometimes stretching regime can involve one not the other...there fore explosive actions using these muscles can cause tears that can be painful...if not too severe one can still manage to walk although longer walks would aggravate...
the other is a claudication... in your case you say you always have it in both calves...and in ur description they seem to be happening at the same time...this may suggest poor circulation coming from more common proximal anatomy of blood supply to both legs...
Claudication should get worse as you walk longer...in your case it feels better walking? perhaps due to collateral circulation working more effeciently in standing...
activities such as cycling, rowing, some body postures in ballet can predispose to arterial occlusion...
I would suggest meeting with your GP and having a doppler done to exclude this secondary reason...