Ok, not wanting to scare you but show your husband this post:
I had a back to back labour.
It lasted 40+ hours from induction to birth.
From the moment I got the pessary inserted, I started with contractions that manifested as back pain. After a few hours, I couldn't sit on a flat surface or lie down without wanting to cry.
Then my waters broke. I was still dressed at the time and had to strip completely, put the wet clothes in a bag (after the midwife had sniffed them to check I hadn't just wet myself 
20 hours later, I'd progressed enough that they moved me to delivery.
The first three contractions with Gas and Air made me convulsively sick.
Then the MW told me not to bother redressing from the waist down, because they were examining me so often and I was tired and sore. So I was sat on an absorbent mat on a birthing ball, half naked.
Then they catheterised me.
Then they moved me to another room and started faffing with blood tests on the baba, so there were a dozen members of staff and me in stirrups with everything on show under surgical lights!
None of this, btw, is that unusual. (And I'm really not trying to scare you - all this sounds horrible but I actually think I had quite a good experience!)
Giving birth is not a spectator sport. You won't care at the time, but you will are later and no-one at the hospital wll thank you for extraneous bodies.
Tell your husband to tell his mother no, now. And if he won't, you need to.
The only people who should be anywhere near you mid-labour are those you choose!