NOT TRYING FOR PREGNANCY at the moment but no periods this month ???

come on April 28 or 29 or even day late or whatever. Today is May 2nd still nothing. It didn't happen with me before. I did pregnancy test May 1st and it says NOT PREGNANT. I have no stress at the moment even instead excited to travel here in few months. We will be trying for it later this year. Not on any birth control, do not use condom just pull out method and we have been using this method since the beginning so 5 yrs. after delivery used condom for good year and half as had csection and don't wanna risk. But now its been 22 months of my csection. Can someone please tell me why this happened to me ? Is it normal? I have one under 2. I am not sure if its hormonal changes or what? I am freaking out here. I didn't consult my family doctor yet .. age is 30. PLEASE HELP highly appreciate your time. Thank you all