It is completely possible you could be pregnant again, as long as you ovulate and were intimate, it's possible. You don't need a period to get pregnant.
You could talk to your doctor about doing a hormone levels test to see why you are not getting pregnant and if nothing is elevated, and you want one now, ask him for provera. I have PCOS and they have to use that to make my body "think" I ovulated and then 4 days after the last pill I get my period.
You could also just be careful if you are not ready for another, and wait it out. My sister had a period after 7 weeks, but my friend went almost 3 months after the birth of her child.