BFN after IUI and delayed period

I Believe 🌈

Had <a href="https://glowing.com/glow-fertility-program">IUI</a> after pregnyl shot on Aug 9th. My period which was usually happen at 26 days has not come till day 28 since last period. I also did a First Response today and it came negative 😰

What should I expect, any tips, I am 41.