MISSED PERIOD HELP!?

Okay so I’m currently 10 days late, I’m usually pretty regular so this is terrifying. I’m not pregnant, I’ve taken two clear blue tests a week apart and no faint lines, one very bold NO. So any ideas what it is? I’m still having period pains but no spotting or bleeding or any kind. I’ve not had any injury or illness recently. I’m really confused. Anyone else been through this?

And yes, me and my partner are very safe so I’m like 99.9% sure it’s not pregnancy 😂