Ive had depo injection twice so ive been on depo 6 months and i was meant to have my third one 2 weeks ago but i missed it, ive had no periods while being on the injection and me and my partner had unprotected sex during the 2 weeks i didnt have it and today ive had light brown blood, could i be pregnant this soon or could it be the injection wearing off? has anyone else had this?