Keep getting BFN

Jossiany • I`m 32 years old. I have been with my husband 11 years years. Now we are ready for a second baby!!
So my period is 13 days late but I keep testing negative. I dont really have any symptoms but for the last week I have been waking up with this excruciating liger back pain that won't let me move for a few seconds. Does anyone knows if this is a pregnancy symptom?