Embarrassing Question Y'all: Vaginal Discharge Question?

First of all I am on the Depo shot (been about two months since my shot but this is the first time using Depo). I am having sex but have been only doing so with the same guy for about 3 years.I went to Mexico for seven days and used the water to wash off. Ever since I first washed off using the water in Mexico I have been having brown, thick, odorless vaginal discharge. I am having no pain, itching, discomfort, or sores. I don't know if it is a serious problem or if it is just from having the Depo shot. Thank you so much for the people that can help!