Going off work

I have my maternity leave date set and will be leaving work at 38 weeks.

I am 30 weeks 4 days and already starting to feel tired, sore feet, and achy back. I come home from work and have to just sit and do nothing to get ready for the next day.

Will doctors give you a note to go on sick leave before maternity leave? Is this something you can ask for or would they have to recommend you stay at home?