I'd stop driving it first off.
That said, is the fluid new? Perhaps it's so cleat that your' not noticing it?
Did you leave the top off and something ( a leave or other matter) got inside?
Do you have good brake pressure?
A "pocket" such as you described should result in spongy brakes as that air would get sucked into the lines and/or the brake pressure tank won;t compress the air.
I'd take the master cylinder off and bench bleed it to be sure. With it off, you might be able to see the problem better.