What Causes Brown Vaginal Discharge After Recovering From Pneumonia?

Hi I'm a 23 year old female generally in good health. However, I had pneumonia for a month and I was on 4 different antibiotics in a month period. I haven't been on antibiotics in about 2-3 weeks and I am due for my period in 1.5 weeks. I am having brown discharge for the past two days with a little bit of itchiness mostly external. I am married been with the guy for 3 years. I am on birth control and have been for about 9 years.