7 weeks postpartum pregnant?

So I am 7 weeks postpartum and still have not had my period. I am not breastfeeding, I have had unprotected sex at 2 1/2 weeks and used pullout method. I went to my ob at 5 weeks for my check up and I had a test it was negative and I also took one a few days ago. I am having a lot of watery cm and cramping. I figured the other day that I was about to start and nothing came not even spotting. I have had 2 negative tests so far. But I don't know what else it could be. I am still wondering if it is a possibility and I can't start the pill until I have my period either so that's another reason why. Has anyone been through what I have and ended up pregnant again?