For better or worse, you've got what you've got. Don't second guess yourself this late in the game, you'll only get stomach ulcers. Yes, make an additional principal payment each month, as much as you can comfortably afford. Be sure the overpayment is applied solely to your principal (check with your lender to be certain). This will save you quite a substantial amount of money in the long term, and perhaps make a huge difference if you need to resell your house due to unforeseen circumstances in the future. Best of luck and congratulations on your new home!