Not sure, are you breastfeeding?

No i'm not breastfeeding. The test I took came out negative.

Ok cause I was going to say breastfeeding an infant tends to delay your periods and helps you not get pg. I haven't had a normal period since before I got pg over 11 months ago. I've had cramping but I think that just might be cause of my operation 2 weeks ago, or ovulating and it not having anywhere to go. But that only lasted a day.
You could just be tired it takes a while to get use to a babys rutine then they change it on you. Have you tried giving her cereal right before bed. That helps them sleep longer at night for you (6-8 hours). That way here soon you can start getting a full 8 hours of sleep. It helps.