It's totally normal. Periods take a while to sort themselves out with all the hormones going back to normal in your body. If you're concerned about getting pregnant I would talk to your doctor about postpartum birth control options, because it can happen. If you are getting a period then you are able to get pregnant. Especially right now when hormones are all messed up.
It can take ur period a little bit after birth to regulate. If the tests are negative but you still think your pregnant you should see your doctor.
Although it can happen and you can definitely be pregnant if you've been having unprotected sex. It is also very normal for a period to come late/ or not even come at all. I didn't get my first period until my daughter was 1 years old
Can take a few cycles for your period to go back to normal...