Your period could return at 6 weeks, or it could take as long as a few months to return to normal. It is not unusual for your body to need a year to adjust - so your periods may be wonky for awhile. -- or, they could just go right back to normal.
Even while I breastfed, I got my period. But my best friend was periodless for more than a year! I was jealous! ;)
you asked in another thread about fertility. You will be fertile at any time after birth - even if your cycle hasn't come back to normal. Use birth control at all times unless you expect to get pregnant.
At your 6 week post partum check up with your doctor, he will discuss birth control options for you. If you plan on going on the pill, this would be a good time to get that prescription!