mini pill & late period

My son was born October 2016. Ive been taking the mini pill since December 2016. In April 2018 I started having periods again. I had two in April but ever since I've had one every month. These are the periods ive had so far.... April 1-6, April 16-20, May 1-6, & June 1-7. I was 3 days late last month but now according to glow I'm 8 days late! I took a test when I was 3 days late (like I was last month) it was negative. Is it possible my levels wasn't high enough yet? I've always found out I was pregnant early on. But now that I'm 5 days later than I was last month when would be a good time to test again? Now? Should I wait a little longer? We wasn't actively trying hence the birth control but would happily welcome baby #3😊