Ah, ok. based on the numbers you've given, your remaining balance is about 129k?
You can't really use original balance / term and current rate to work out your repayment amount.
Unless the interest rate had always been 3.7% the rate at which you paid off capital would lead to a different repayment amount now.
If interest rates had been higher on average since you drew down, you've paid more interest and less capital than if it'd always been 3.7%. So your balance would be higher now requiring larger repayments to cover it over the remaining term.
Does that make sense?