Scared, very heavy period with intense cramping?

I had been spotting for about a week before my period started to come on last night. It is so heavy, I have gone through about 5 super sized tampons within a 4 hour period, not counting all the blood that has escaped. I am having to change my tampon atleast every 30 minutes. When the tampon becomes soaked it just pours out of me or steadily drips out of me. I have soaked several pads and had to change my shorts 3 times just in 4 hours . I have very cramping that is enough is to double me over and cry. I have irregular period and irregular ovulation, I do believe I ovulated with this period. We have been trying for a baby and not sure if this could be a miscarriage as I have never knowingly had one. I did take a hpt the first day I began spotting and it was BFN. Also, what are the warning signs of becoming anemic?