Depo pregnancy, and IBS

katie
I recieved my second depo shot on September 10th, 2014, ever since then I've been having unprotected sex (he never has ejaculated inside me ever though) But I haven't had a period at all since the second shot. I also happen to have IBS-C and an extreme case of bloating for about a few months now. I wake up skinny but by the time I got to bed, I look 10 weeks pregnant. I've been having dizziness everyday, nausea, headaches. Im not sure if it's the IBS or if I really am pregnant. I'm scared. I'm only 16 and I'm terrified of any kind of surgery, I can barely stand shots. Should I take the next step and get a home pregnancy test, or is the chance too slim? I'm terrified. :(