depo shot help

I've been on depo shot for about 2 and a half months , I'm supposed to get my next shot on the 14th of feb . I haven't had any bleeding since the shot but today I am sick and had some very sharp pains in my stomach and now heavy bleeding for the past hour. What's going on? Last month took a pregnancy test just to check because I was feeling sick and having cramps the first had two very faint lines the next two were negative.Update:fever of 100.3