6 days late...no pms symptoms..

Hi everyone, last monthI did an hsg test to see if my tubes were blocked. Everything seems fine! The doctor told me I had a higher chance of getting pregnant that month since everything was kind of cleaned out. So I was super dissapointed when I got my period. I was kinda done with it. Did not log my period, didn’t do ovulation tests or anything. Yesterday I decided to look in my app since I was wondering when I should get my period this month. App says I’m 6 days late. My period is regular so since I didnt log my first day of period last month let’s say I’m between 4 and 7 days late. No pms symptoms whatsoever and still getting negative pregancy tests. Any of you experienced this?