Could I be Pregnant 😩

So before my son was born my periods were normal and regular.  They always came on time and ended on time.  About 3 months after my son was born I went and got my birth control shot..... after that my periods were irregular which I expected.  I never got my second shot and my periods continued to be irregular.  I had my last period for a few days and then it stopped for a couple days and started again for a few days..... based on this app I should have started my period about a week ago.  I took a pregnancy test a few days ago and it was negative.  Thinking about taking another one just to be sure.  Yes I have been sexually active and my husband always pulls out.  I know it's possible for me to be pregnant but what are the odds 😩 I'm not financially ready for another baby right now