I am 18 and have been having a few problems and I am wandering if I could possibly be pregnant. I was put on the birth control shot in May and that was the only time I took it. I am sexualy active and I haven't been having my period right. For the three months that the shot was supposed to work for all I done was spotted. Here lately every few weeks I get back pains and have gas all throughout the day. This has been going on for about a month now and the pains and gas last for about a week and during that same time I spot but its brown. And I have put on a little weight and my appetite has went down and I have been drinking more liquids than usual. I was wandering if you could maybe give me and idea of what's going on and what I should do.