been off depo a little over a month....

I got off depo due to the side affects i didn't like them at all. I was on it for 6months. well i just had like a 14 day period or atleast thats whay i think it was. some days were lighter than others. i did have sex and now im worried if being pregnant is possible.... i stopped bleeding 2 days ago but have been having brown discharge or blood im not sure. so im just so confused if it could just be my body trying to get back to normal. im also having cramps.... has this happend to anyone......