If you've made purchases since doing the balance transfer then you'll be paying interest on that element as the payments are allocated against the balance transfer part.
In order to see a reduction you'll need to start paying more off than just the minimum each month. Even with 0% you won't reduce the balance much if you keep to the minimums (unless you're stoozing and earning interest on the extra payments you can afford). You need to find more income or reduce your expenditure and get the balance down.
Credits cards aren't designed to be long term credit solutions - they are designed to be carry balances for one or two months maximum and then be paid in full.