What Are The Signs Of Fertility When Still Breastfeeding?

I asked a similar question a while back in regards to using breastfeeding as birth control, but today I have a quesiton about some mild cramps I have been recently having and wonder if they could be a sign of my fertilty trying to come back.
I have three children. With my first son it took me 3 months after I quit nursing for me to have a period. With my second son I got pregnant 2 weeks after I quite breastfeeding without ever having had my period (yes i know you ovulate before a true period). I am now nursing my 10 month old son. Do your periods resume earlier with each pregnancy? I have not had a period yet, but yesterday I did have mild cramps. Anyone else had a similar experience? Do cramps mean that the return of my fertilty and periods are around the corner or are my hormones just out of wack?