Feeling defeated on DPIUI 11 with BFN

I had my (37f) first IUI on December 18th, trigger (ovadril) Dec 17th, (Letrozole+menopur shot, then progesterone after). Everything went well, I had two good follicles and my husband's sample was good (58 million after wash and 51% motility). I was feeling off, crampy, a bit nauseous on DPIUI 9 and then my BBT was a bit lower DPIUI 10, it was back up this morning (DPIUI 11) and I was feeling optimistic that it was from implantation but when I tested I got a BFN and now I'm feeling like I am out for this cycle.

Logically I know it is still early, but I am so bummed. I was using an early detection test which detect HCG at 10 mIU/mL (regular tests it's 25). I had two CP earlier this year and tested positive for those on DPO 10 and 11 respectively, which I feel like is adding to my disappointment.

My clinic wants me to keep taking progesterone until I get bloodwork done by them, but because of the holiday and the weekend, that won't be until Monday Jan 5th, DPIUI 18, I am just dreading dragging this process out for an extra 4 days.

Any stories of late positives or words of encouragement appreciated.