First, you really should get off bc pills if you are trying to clear out candida. They promote candida growth by messing with the hormones. For me, it seems that going on bc pills turned my borderline case into a full blown problem.
Second, if 3-lac is killing candida, your liver has to work to get the resulting toxins out. A toxic liver will often mess up your cycle. So yes, it is entirely possible that the 3-lac is causing your fluctuations. But, like I said, I would be much more inlcined to give up the bc pills than the stuff that is working to heal you,