Welcome to HCM
You are diabetic well controlled on metformin and exercise and diet ,yet how long diabetes is there , what is your age and are you overweight and also important to know smoking and alcohol use.
In patients like you leg pain may be manifestation of developing neuropathy,as you walk so much another possibility is muscular pain
which may be complicated by vitamin B12 deficiency
and side effect of metformin like lactic acidosis
You can consult a Neurophysician and get Nerve conduction study
to know the cause .
Good Luck to you