Can a gyn check if i have a yeast or bactearia while am on ma period?

Yes, but can be diff: Yes, but it can be more difficult. Depending on the condition of the vagina and vulva (more redness, swelling and pain with touch), sometimes one can diagnose a yeast or bacterial vaginitis even when on your period. Having said that, it's possible that if the flow is heavy and there aren't changes in the epithelium (skin) of the vagina or vulva it can be more difficult.