Implantation or period?

[annalise214]

I am currently on birth control (microgestin) that I began taking in October. I missed the fourth day of my first week two weeks ago and did not remember until my next dose, so I skipped it. I had unprotected sex with my husband within that time period. I bled heavily for about 2.5 days due to missing my dose and then it ended.

In the past week, I have not been feeling well. My lower back has been aching, and I have been abnormally fatigued and emotional. Two nights ago, I had an intense lower back and abdomen cramp and bled out a little bit of old blood. Cramping has continued and I was bleeding black/brown blood until last night, when I bled some bright red.

Any idea what this is? Implantation, miscarry, random period?