With ds, my period came back at around 10-11 months. This time round, I was feeling ovulation pains a month after giving birth, AF came back at around 3 months, I think. Kate was having long stretches of night sleep at that age, up to 10 hours, and even though I was getting up to pump, it was just not enough. We also were having long stretches during the day when she would refuse to feed, due to reflux.
At ovulation, I would notice an increase in supply, and then had a real dip for almost a week during AF. Kate is almost 8 months now, on meds for reflux and feeding better. I also had to eliminate the cluster feed before bed, which she used to do, so that brought back a night feed for us. Those night feeds were crucial for me to keep my supply up. Since she started night feeding again, my period has not come back. Other Moms seem to have no issues even with AF and no night feeds, it is a very individual thing.
What is your baby's typical feeding pattern like? If weight gain etc is good, then that's a relief anyway.
I found this info useful
http://www.breastfeed-essentials.com/menstruation.html