What Causes Abdominal Cramping And Missed Period With History Of Ectopic Pregnancy?

I have not had a period in over a month. I have taken several pregnancy tests that have all come out negative. I do get night sweats.
I have had some very mild cramping but only for an evening or two. No sickness.
I've been sleeping a lot but my jobs heavy irregular hours can be the cause of that.
I have had a tubal pregnancy in 2005 that almost cost me my life. I have not been pregnant since.