Like JohnT said, you need to aerate your water to bring your pH back up. Here's the link to the proper way to lower your TA without completely bottoming out your pH with all that acid, for the next time you need it.
http://www.poolforum.com/pf2/showthread.php?t=191

A FC of 3 and a CC of 5 sound a little suspicious to me, it would be a little more believeable if the numbers were reversed. However, the fix is stil the same...you need to get some bleach in there, raise your Cl level to 12-15, and keep it there until your CC reading is zero.

Your CYA container will have doseage information on the label--20-40 ppm CYA is a good number to shoot for, but I would only add half the dose at first, either through the skimmer (don't backwash or retest for at least a week, since it takes 4-6 days to dissolve) or in a tied sock in front of your return stream.

Janet