Almost every month, for the past 6 months, I've gotten yeast infections either right before my cycle or right after. Is this common?

Your condition is not uncommon, but any immune deficiency like diabetes will cause this to be a chronic condition. Do you have MS or diabetes? If not then your chronic yeast infection condition is probably caused by an improperly balanced Ph system in your vaginal tract. This can happen because of constant douching with any substance as this destroys the natural cleansing balance there that we women have. Or, rough sex and foreplay can be the culprit too. Have you been taking antibiotics on a constant basis; this would interrupt your system as well.