I'm 35w too, almost 36w, and feel exactly the same.
The past two weeks i've been really struggling to make conversation, my brain feels all over the place, I also can't concentrate either so you're not alone on that front.
I'm sure your mum will understand if you say you're feeling especially tired with packing for the house move and getting ready for baby, so aren't feeling upto it, but maybe she could pop for an hour at your house if she really wants rather than you having to go out.
A house move is stressful enough never mind adding prepping for a new baby in the mix, if someone doesn't understand that then they are the terrible person, not you.
My mum also asked to come this weekend as it's her birthday, I obviously didn't want to say no, as I do normally make a big fuss for her. She's so excited about the baby (family's first grandchild), but this pregnancy has been anything but smooth sailing and currently in hospital 3x per week for monitoring, it's hard to be around someone excited and bouncy like she is when my emotions are all over the place with worry/stress. I know she's going to ask a million questions about baby/hospital/the birth, but i'm just going to change the subject and keep things light.
So don't feel terrible, make sure you advocate for yourself and rest when you need to, please don't try to please other people and end up getting run down because of it.