J.F.
You could simply just not be having a period because of sporadic hormones. My periods came about 2 months after I had my daughter, but.... she's almost 3 now and I haven't had a period for 6 months, and I'm NOT pregnant! Do you have a history of missing periods?
Oh, and the pull out method doesn't work. A little bit of cum comes out before the actual "go". So, I would use condoms for the time being.