The only one time ive ever used birth control was after my third son was born. I got the depo shot 2 days after he was born on October 31, 2013. I did NOT ever go back to get any more shots. Since then (besides the bleeding from after pregnancy) i havent had a single drop of blood or period since, and last night 1/23/15 i finally noticed a very light brownish-pink color in my underwear, wiped myself and saw a little on the toilet paper. Today, 1/24/15, there was a little bit more but didn't last longer than an hour, and is now darker brown. I have had unprotected sex in the past few weeks multiple times but its hard to tell if this is the start of my first period or if it could be implantation bleeding. Could this be possible even though i havent had my first period back yet? Any help is appreciated!