Gardnerella is not really an infection - its generally called bacterial vaginosis, and its an over growth of the low levels of vaginal flora....i can't see how the antibiotic treatment would cause you to bleed. Its a vaginal infection - it doesn't actually ascend past the cervix.

As for whether your pregnant - you can't tell by the CM lovey. All you can really do is wait to see what the doc tells you, or do a HPT