I am 24 years old. Had my tubes clamped almost 3 years ago (in April) during a C-section. I keep very good track of my menstrual cycle, and i am an average of 28-29 days with periods lasting 6 days. Always a fairly heavy flow (filling a tampon in 2 hours) 2 days before my period was due i had a faint tinge of blood when wiping, then nothing at all again until i was 4 days late. At this time was the same thing (just enough when i wiped a couple times, no pad) then on 5 days late this happened 3 times. ( about half teaspoon full at a time, then nothing for hours in between) then today at 6 days late i have has a trickle most of the day off and on. I am very nauseated to the point i dont want to eat. I normally have stomach cramps during menstruation for maybe 20 mins or so, but i have been cramping off and on all week, and ALL day today, including very bad lower back cramps that radiate up to mid back. Feel very tired/ week also. Have taken 3 pregnancy tests through the, all negative. What could this be!?