In 52-14, with a reasonable cadence of 90rpm, you would be riding at 26+ mph on 700c wheels with 23mm tires. I find it rather unlikely that you ride at such a speed "all the time on flat terrain in non windy conditions."

I'm guessing that you are rather new to cycling and are still pedaling at a painfully low cadence. You don't need higher gears; you need to learn how to spin. Your knees will thank me when you are...my age.