Diamicron which contains Gliclazide, is probably the reason, if your dose has been increased. Walking will help with BG levels but I wouldn't like to say by how much (couldn't say by how much), my father's experience was that when he stopped walking (leg muscle pain. statins? being 87?), his BG was all over the place and he has never had good control since.
Metformin, which you don't mention Kaha, is quite often prescribed as the first line drug of choice especially if the patient is overweight or if insulin resistance is suspected. I'm not sure why there's a suggestion that Metformin "helps a bit but not much". It is also chemically synthesized.