At what point did you feel too tired to carry on as normal?

This might apply more to people in the UK or areas that pay maternity pay as I'm aware that a lot of counties have to work up until giving birth.
But I have 3 weeks to go until my due date, I'm on maternity leave but I'm really struggling to sleep and I'm just so tired! I have people wanting to visit me or go out for meals etc and I just feel like I want to say no to them all and hibernate!
Am I being a bit dramatic? Did anyone else feel like this towards the end of their pregnancy?