hello, I have had a regular period for the past 7 years. i had one 8 days late for the first time ever in january, but i just had spotting. two periods later, i ve only had spotting each time i was scheduled to menstrate. I ve taken 3 home pregnancy tests , and a blood test, all of which have come back negative. I ve had symptoms including lower back pain , slight nausea, extremely frequent urination , acne (never experienced prior) and uterine cramps. what do you think could explain these things? thank you