Wow you're having a rough time ! Hugs for you if you want them.
I don't have much to give you, just the fact that it's more than normal to be fed up/tired/depressed with everything you've been through in the past couple of years. So don't feel bad or inadequate about having those thoughts/feelings. I'm fed up with pregnancy too and I'm having (so far) an easier time than you ! It's not about how much you love or want your baby, it's about how hard this is on you physically and emotionally. The fact that it'll be worth it ultimately doesn't make it easier right now.
Can you ask that another midwife be assigned to you ? The one you have doesn't sound like a good fit for you.
Is it possible to find another solution for your laptop ? Maybe you can get a new table/desk or chair that'd be comfortable ? Even if you have to order from Ikea or whatever, that might be worth it ?
Finally, can you speak to your manager and involve HR so your workload can be adjusted, even if only temporarily ? Obviously I don't know how reasonable your organisation is, but it's definitely a reasonable thing to ask.
If they are in the less reasonable category, maybe just tell them "okay, we need to talk about my workload ; I can get X and Y done this week but I'm going to need more time to finish Z. Any specific priorities I should focus on ?"
Don't tell them why it can't be done (exhaustion, depression, etc) if you think they would hold that against you, just stick to the salient point - it'll be done on a different timescale.
Try and take good care of yourself and don't have excessive expectations. You're pregnant and tired. The housework can wait, and your partner can pull his weight (assuming you live with someone).
No advice for the HG, my SIL has this and I know she had a really hard time (still does). She said she picked what food to eat on the basis of how it tastes when it comes back up !
Please feel free to vent on here if it helps at all !