L.R.
It is common to have very light periods when on BC and some birth control's causes periods to be so light that eventually you might not have one at all. If you are not pregnant then your BC is doing an excellent job of suppressing your ovaries, which is what it is supposed to do in the first place. So enjoy it if you can, however, since you feel so concerned it would be worth a call to your doctor to confirm that he/she feels it is normal for the type of BC you use. I don't believe that a yeast infection should affect your period. Good luck!