C.F.
With my first daughter, we breastfed until around 15 months. I didn't get my period back with her until I stopped nursing completely. I also did go back on the pill at 6 weeks (using micronor, very low dosage) and still never had a period, which quite frankly, was very nice.
My second daughter is now almost three months, and I started using the pill again at 6 weeks (same one I used with my first daughter). My period came back as soon as I started taking them! And it was 10 times worse than I have ever experienced in my life. I had the worst cramps and headache and had to use a heating pad for two days.
I guess my point is that every mom is different, and it's different with each child you have. Hope this helps :-)