I could have written your post a couple months ago! It's so frustrating when you really want to conceive but your darned periods won't come back. I got my first pp period when my dd was 22 mo, then got pg the following month.
Have you been to the "TTC and Infertility" boards? There's a thread there for mamas like you titled something like "nursing mamas ttc" or "for those who *want* AF to come back" or something..