menstrual cycle after birth

I gave birth on Sept. 10, breastfed until Nov. 22, and my menstrual cycle started again on Dec. 17.  Now it has been one month and no signs of my next cycle.  I have taken 2 tests , one on the 15th and 13th of Jan., both of which were negative.  Does it take more than a month for your cycle to get regular again?  I am an otherwise healthy 27 year old woman praying to not be pregnant again.

[Me2mommy2b]

I was told that menstrual cycle takes time to regulate so it doesn't necessarily means that you're pregnant.  That's why you need to be more careful if you don't want to be pregnant b/c you can't tell when you're ovulating.