Late with lower back pain

Nm

Last month I was 6 days late with lots of lower back pain on my right side, AF showed up on the 7 th day and the back pain stopped. This month I started having the back pain again just after my ovulation and now am 2 days late and tested this morning with clear blue, got a negative.

I am slightly worried that the pain is connected to my late periods and yet negative results. Anyone experienced this before?