2 days late bfn - am I out?

Hey ladies, I need help!
I have a 28 cycle, and I am NEVER late. 
Right now I'm 2 days late. I've had light brown spotting the past 2 days, but no red blood. 
I have terrible periods (killer cramps, bleed like a stuck pig, and feel horrible), but I feel completely normal. Light cramps today, but that's all. 
I had PMS as usual (moody, big boobs), but it all stopped yesterday. 
I tested yesterday morning -- negative. 
Is it possible I'm pregnant? Or just wishful thinking. 
My husband and I scheduled our 1st <a href="https://glowing.com/glow-fertility-program">IUI</a> for this month (we've been ttc for 2 years) and this is a shitty month to have a wonky period. 
Let me know what you think!! =] Thank you!