Maybe by keeping the power in, you've actually added too much thrust and kept the airspeed too high, in which regardless of how you flare, you have too much lift!!!! Controlling the trade-off of pitch for airspeed, power for descent-rate is critical here. If you're in a C172, add maybe 5 kts at most for a fully loaded plane vs. you solo, anything more is going to cause float and other problems.