There is a bug going around that feels similar to menstral cramps. It has hit a few people that I know including myself. I think I had it the longest of anyone, about a week and a half or so, and I still have a little of the cramping feeling but not as bad. My husband got it the easiest only a day for him. This also included the loose stools which also can come with the period stuff. And I felt a little queasy too.
On the returning of menstruation after pregnancy and breastfeeding issue - my daughter was almost two years old before I started again. It was great! three years with out the period or mood swings!! But they are still not regular, I quit nursing her at 2 1/2 wich was about two months ago.