Delayed period !!!

Can someone please help me!!

So i was taking BC from sept 2018 till Jan2019.. i stopped taking it and my periods were very regular.. tho before i had my child i was irregular.. well i had my period june 2nd till june 7th i then had unprotected intercourse on June 9th & he finished in me... i am now 4 days late in my period.. and i am freaking out!! I have been 2-3 days late before but 4 is just freaking me out!! I have mild cramps, lower back pain, and stomache tightening feeling.. i did a pregnancy test when i was 2 days late and came out negative.. is it normal for my period to be delayed.. or did i check too early for pregnancy?? Ohh the last time i had sex was june 9th , i was not ovulating.. had just finished my period 2 days before intercourse..