Spotting versus period start

Weird question. My periods are always light because I’m on birth control. Sometimes I have break through bleeding/spotting on the birth control, which I’ve been having this week. I stopped the active pills 2 days ago, which means normally I would get my period tomorrow, but it can vary a little. I need to know what day it has started because we are starting <a href="https://glowing.com/glow-fertility-program">IVF</a> and I need to notify the clinic.

It sounds stupid but I’m not really sure how to differentiate between spotting and my period start. I’ve been having a little bit of bleeding every time I’ve gone to the bathroom today, but it’s pretty light. I’m not quite sure if this is spotting or if I should consider it the start of my cycle. Any advice?