What is going on today?!

I’m 36+3. Overall I’ve had a great pregnancy and can’t complain.

I don’t know what is going on today, but I feel extremely exhausted. I can barely move my body or do anything. Just very lethargic. My hips and knees feel like they are going to just fall off.

I am already taking extra iron for anemia for over a month now. The only reason I feel concern is because I have not felt like this at all before today - such a sudden change.

Anyone else experiencing this? Any words of advice? Should I be concerned?