Hello,
None of your footwear/orthoses are new are they? Or were they in December? Sometimes this can cause problems with the slight changes in biomechanics, as the body takes a little while to get used to the new positions.
You didn't mention whether your sports therapist gave you any stretching or rehab program at all? Are you currently doing any stretches specifically for your calf region?
Also you might want to have your hip/knee/ankle assessed if not done already to see if there's anything going on further up the leg which could either cause an imbalance, or be referring pain down into your calf.
Given that it is recurring it seems it's either a strain which is not recovering fully, or there is something which is not quite right perhaps biomechanically that is causing the injury.
Hope you get it sorted out!
Ruth Cheesley BSc(Hons) MSc MCSP
Chartered Physiotherapist