What Causes A Vaginal Discharge With No Odor?

Hi I keep getting this brown discharge, it dosen't smell, its happened recently and I don't no why. I'm in a healthy relationship with my boyfriend, We have unprotected sex on occasions but he never ''comes'' in me. I had a period about a week ago it lasted only about 3days so I don't think it could be pregnancy I'm not sure I would just like some advice what to do? Thanks