Strange test results -- very high combined chlorine (CC)

[Themadczar]

I don't get it... Both my fc and cc are staying pretty consistent, but they are still not where they should be. Since getting home from vacation, fc isn't dropping below 4, but cc is staying in the high teens. See below...

Date_ time_ FC_ pH_ CC

2013-06-23_ 00:10_ 5.0_ 7.7_ 18.5
2013-06-23_ 19:05_ 6.0_ 7.7_ 12.5_ added 384oz 6% bleach
2013-06-24_ 18:13_ 4.5_ 7.7_ 19.0
2013-06-25_ 19:42_ 4.5_ 7.7_ 16.0_ added 192oz 6% bleach (1/2 dose since already over 20ppm)
2013-06-26_ 17:38_ 4.5_ 7.7_ 19.5_ added 192oz 6% bleach (1/2 dose since already over 20ppm)
2013-06-27_ 18:58_ 5.0_ 7.8_ 19.0

I can't add more bleach (already over 20ppm tc), but doesn't seem to be making progress either. And ph has creeped up to 7.8. Any idea what I should be doing at this point? This is getting really frustrating. Pool open for over 2 months and we still can't swim in it.