@Dala Barnes,
What were you shooting?
Some find their accuracy goes down the longer they practice.
A hand gun may not seem very heavy, but prolonged periods of time held at that position can induce muscle fatigue. Especially if you are not used to holding that position on a regular basis.
I have a good friend who used to be a really great shot. Then he got in a motorcycle accident. Now, he can only shot about a dozen times (from the prone) before his back hurts to much to hold the position.