Bit late now, but in case anyone is interested, Kellymom has an interesting article on
breastfeeding and fertility that makes for an interesting read.
The thing about periods is that they can be all over the shop. Anything that is 6-8 weeks post birth is classed as lochia, even if it has previously stopped and it's actually quite rare, if you are bf, to get them back before 8 weeks. Having said that, mine came back really early with DS1 (think it was technically 12 weeks) as I was bleeding FOREVER after he was born. Having said that, the first 2-3 months post birth is when you are hyper fertile, as Britney Spears and a mum in my antenatal/coffee group found to their cost!
With DS2, it was 11 months and feeding was erratic to say the least in that he'd dropped night feeds at 7 months, then they were back 3 weeks later! I felt "different" from about 9 months though and thought that it was going to put in an appearance, but it took a further 2 months. First one was fine, second one was atrocious (started on his first bday no less!) with heavy bleeding for a week and minimal bleeding for nearly another week!!!

I ma now waiting for the third, which is technically a day late, but finally went on the mini-pill last month and that has always made me very irregular.