Yes, it is totally normal! And it is safe to do omad while menstruating, although much harder.
Your body basically says: I am preparing myself for a theoretical baby. I don’t know if I got pregnant, but let’s be careful and start preparing to feed the non-existing child just yet.
Just be a little kind and patient with your body and if it works for you do some 16:8 if you feel better through the difficult time.
Remember: losing weight is a marathon, not a sprint. So be kind to yourself and stay on track.I’ve found that staying on track is easier when you are kind to yourself.