Hey Baby-
I didn't breastfeed or pump, but I was one of the unfortunate ones who started my regular periods very shortly after giving birth. I only bled for about 8 days after giving birth to both of my childred, and then my regular period started 3 weeks after that. Both times.
I don't know if this has anything to do with it, but I've always had a period every 21-22 days. (short cycle, urgh...) Were you on the pill before concieving or not? Also, before going on birth control (if you were on it) did you have a short cycle? Maybe it could have something to do with it??? Not sure, but that question just hit me while reading your post.
Our bodies are something else, aren't they?!?