TTC and a week late!

Ny husband and I are TTC. I've been off birth control for 4 months now.  The first three months I never ovulated that I know of, but after
My last period I finally ovulated. I've always had very regular periods but as of today I'm a week late. I've tested 3 times and all are negative. Do you think I'm pregnant with low HCG or could my ovulating have caused my period to get pushed back??