False negative?

Tisha • Disney fan with loving husband, trying for baby #1

I took a pregnancy test with clear blue and it came out not pregnant... But according to my chart and how my body works I should've had my period on the 23

I'm now almost 2 weeks late and have been having my regular period symptoms since before I was supposed to have it but no period. I changed my meds so maybe that's it? Has anyone ever had a false negative?