Hi I'm A 17 Year Old Girl. For The Past

Hi I'm a 17 year old girl. For the past month I've had serious pains in my lower stomach and sides almost like cramps but I'm on the Depo shot for my skin so they can't be cramps. I also found a dark spot on my lower stomach. It doesn't hurt but the other pains are still there. I need to know if it could be serious and if I need to seek medical help.