Advice for birth control?

I'm 17, and when me and my boyfriend got together in May I got my first Depo shot, which lasts for 3 months per injection. It was fine for about a week and then I started bleeding like crazy for about two and a half months solid (it'd stop for a day or two every couple weeks) but then after that and once I got my second shot I just started getting a lot of spotting and my discharge is usually a red/pink colour and on occsasion it smells really bad. I also don't really get a proper period anymore because I'm lightly bleeding a lot of the time. We ALWAYS use condoms no matter what but I was wondering if anybody had some advice for me? The injection I have now runs out in two weeks.. Should I get the next one?