The Shot

Alright ladies so I am currently on the depo shot and about to get my second round of the shot come mid February. I have also previously been on the shot a little over a year ago and then stopped it. But now I've been experiencing brown discharge everyday for the past couple of weeks. I have to change my underwear 3-4 time a day that's how much there is. This has never happened before jut wanting to know if this is normal or not. Thanks!