Yes! I felt the same for you!
They are all absolutely taking advantage of you...
and as for your DM's comments? What is she thinking? She ought to have your back. Her comments make me think that your side of the family are also overbearing.
I'm betting that you did protest.. and said things like I need to put the kids to bed and that's when they made comments about fixed bedtimes.. because it didn't suit them.
Your DH thinks this is fine because it's fun for him He gets to be Mr Popular and he's not stuck doing all the work. You have a Mary and Martha scenario going on. I feel for you.
Really when I saw your update that they have a family whatsApp and you are excluded... I'd be wanting a look at that.. and checking that your DH hadn't carelessly invited them. He is able to do that because you do all the work and he doesn't seem to have an awareness of how inconvenient it is.
So either use his phone and say its you.. and then set up your own whatsapp and invite them.. say that this is the whatsapp to use to make arrangements for meeting up from now on!!! If you feel they are not listening to you.. you need to send a polite but firm text to all of them. And reinforce it. Don't wait for your spineless DH to speak to them. Its gone beyond that.
Dear SILs.
"You know I love seeing you all but please don't just turn up for an impromptu party without any warning.
I longing for a rest this weekend but in the end we had my two kids, and 6 nephews and nieces running around until 9.30 pm. I've had loads of medical appointments this week and I'm tired out and I just can't cope with surprise entertaining and all the clearing up that entails at the moment.
I do want the cousins to have fun together and am happy to meet at a park or cafe so we can all see each other there, but I am asking you to very kindly not turn up at the house at the moment. I don't want to be in a situation where I have to turn family away but I need all the rest I can get at the moment. "
Send it out.. and if they query it.. follow up with. "You may laugh but I found several of the little darlings jumping on my freshly changed sheets in their shoes. I struggled with a sore back to do it as I was longing to get an early night. I don't think it's fair to allow them to roam around my bedroom and I don't want to see them playing in there again."
I've had to do this.. DH had a habit of constantly inviting people without checking... you know on my one day off when I had plans to do things with the DC, or the weekend before GCSEs started etc. After that I had no worries about ringing them up directly and saying don't come it's inconvenient... let's arrange it for a better time.
You may get push back and be labelled the Baddy or precious. But they have NO qualms about walking all over and offending you and making crap comments. So own being the Baddy.. "Say yes I am really precious but I don't like kids running amuck in my bedroom.I don't let mine do that in your house."
None of this lot have any consideration for you ... You need to sit that oblivious DH down and tell him in no uncertain terms that your health is a priority.. you need rest on doctors advice and if that lot want a party with free childcare they can organise it themselves. The cheek!! Does he come to appointments with you? I'd be telling the Midwives privately beforehand to give him a full on lecture and insist that you must get more rest. And prepare DH for the fact that if they turn up he will be taking them and the kids to a local park/cafe/play area or back to their house and that you will not be moving on this.
I think if you've been in families that boss you around and don't listen to you, it is extra hard to make a stand, but when you have children it becomes a bit easier because you are advocating for them not just yourself. Just keep repeating your short clear very reasonable statements (which are not apologetic or full of excuses they can pick apart ) and you are not going to cave because they mock you. They are NOT the boss of you. They are all organising everything to suit themselves. It's so selfish. Practice saying "No. I'm not doing that. I'm doing xyz instead." and repeat it.
You don't want your kids to be cranky and miserable because they've been running around and not going to bed until after 9,30 pm. You deserve to have time to sort out your household and to look after your health and your baby's health in late pregnancy so its time to put your foot down. These requirements are not unreasonable. If they want to kick off and complain.. Good. Let them! What's the worst that can happen?