IUI -no surge

Hello all, not sure if anyone will know anything about this, but here it goes:
I am in a same-sex marriage and TTC. We did 3 <a href="https://glowing.com/glow-fertility-program">IUI</a>'s and got pregnant on the 3rd. Unfortunately, we had a miscarriage at 11 weeks. I had to have a D&C in early May.
I have been anxiously waiting to get back in the game. I take letrazole each cycle and so far, that has done the trick. This cycle was my first cycle TTC after the miscarriage. I have been using OPK's and typically surge on day 14 or 15. On day 15, all signs were pointing to surge. I use clear blue digital tests, and kept on getting negatives. I was testing every 4 hours! The lines got extremely close in darkness and I would have sworn they were positive, but digital reader kept saying negative. I then had strong cramps on the left side from 2pm until I fell asleep at 10pm. Everything seemed normal except the tests were negative. I called my clinic and they told me I could do the <a href="https://glowing.com/glow-fertility-program">IUI</a> if I wanted to. I decided to go ahead with the <a href="https://glowing.com/glow-fertility-program">IUI</a> because the cramps were so convincing. Anyone have any experience with having all signs of ovulation, but negative OPK's? Trying to be optimistic and hoping I didn't just waste $1200 with no egg in there waiting for it.