The same thing happened to me...I got (what I assuemd) were light periods at 7 and 9 weeks post-partum. However, since then, no sign of AF, and Aaron's now 4 months. I actually got so paranoid I did a p/g test last week, since I thought once it started back it would be regular. Evidently, the b/f does all kinds of weird things and regularity isn't to be expected.
On the other hand, you do have to assume you're fertile now!
Mama to Aaron, 1/26/03