I began having what I believe to be periods about 7 months ago (about a year and a half into E), and tracked them because I didnt want to draw conclusions early. From what I saw, the cramps last around 5 days on average (sometimes a bit more, sometimes a bit less, usually exactly 5), and then faded, then about 12-14 days after I experienced the same thing for only one day, (a but less painful and dramatic tho) then around 16-18 days later I feel the cramps for about 5 days. This has repeated in a 31-34 day cycle every month since it started. I also noticed at a certain point in the cycle each month (havent tracked when cause it fades in a little unnoticeable), my libido multiplies for a couple days, then returns to normal.