5 days late. No AF in sight.

AF has ALWAYS been super regular. The only time I've ever been late was when I was pregnant with my son 14 years ago. I have only been using the app to estimate ovulation, since AF comes EVERY 28 days. I am now 5 days late. I took a test 3 days ago, but it was negative. I searched for a faint line, hoping it was there, but nothing. Ive not had any symptoms of AF. But I've also not had any real symptoms of pregnancy, other than a late period and being tired. Is it too early to test? Should I retest?