Suggest Treatment For Delay In Periods Despite A Negative UPT

I have an unusual period. It usually skips a month or two in between periods. But I have not had a period for 6 and a half months now. I took pregnancy test (2 or 3) about every other month just to make sure I was not pregnant. They all came out negative. It has been almost two months since the last time I have taken one. And last week I would get really nauseous every couple of hours every single day. Right after I could feel myself getting nauseous I would feel my body get extremely hot and I would start to run a fever but then it would go away along with the nausea in about half an hour. Then yesterday the nausea stopped finally but I started to get really bad cramps and brown spotting. Today I have awfully painful cramps, lower back pain, and lots of blood discharge. My question is, am I just having a severe period due to not having one for 6 and a half months? Or does the fact that I was super nauseous that week mean I am having a miscarriage?