5 days late and negative HPT. Has anyone else tested negative this late and turned out to be pregnant??

Meg
Hi ladies! So I'm kind of going crazy. I'm 5 days late as of today (25 day cycle, like clockwork, latest I've ever been has been 1 day). I did <a href="https://glowing.com/glow-fertility-program">IUI</a> this cycle and am 18 DPO.
Took HPTs the last 3 mornings in a row (first urine of the day) and all have been negative. No AF, no PMS symptoms (which I usually have).
I'm going crazy!! Is there a chance I could still be pregnant even with a HPT being negative this late? Has anyone else tested negative days after AF was due and turned out to be pregnant?