14 days late/missed period - Reasons for missed period?

LC • 39 years old

Hi laddies, my periods are always constant every month. I’ve take many test and they’re all negative. I feel confident that I’m not pregnant due to no pregnancy symptoms. I’m a mom of 4 and with my pregnancies I start getting a faint positive at 8dpo.

Any ideas of what can cause me to miss a period. Im terrible worried about potential health issue causing this? I don’t understand , this has never happened to me before.