You poor thing, your pregnancy sounds dreadful!
My DS is now 27 months and I remember being nervous about being away from work (I'm an anaesthetist and it took 15 years of hard work to get where I am). My pregnancy was hideous with fatigue, continuous nausea (except a fantastic 2 week break in the 2nd trimester) and generally wanting to get the baby out ASAP! But I was nowhere close to your suffering and didn't have Spd.
I finished work at 37 weeks and the dratted child was 13 days late! The bit before the baby comes is hard, really good to make a few plans, lunch-dates etc to keep you occupied. Also, do some of the organisational stuff that requires little physical effort - order birthday/Christmas presents for the next 6 months and wrap them, do your tax return, find a cleaner and get them to start (if not already), get and wash clothes for baby up to 6 months if possible, find out about all possible baby clubs etc...
Once baby is born you will feel sooooo much better. My DS didn't sleep and I had maybe 3-4 hours sleep in 24 hours for months, but at no time did I ever feel as bad as when I was pregnant. Everyone said, if you think pg is hard, just wait til the baby is born. Not true. It's exhaustingly but your just tired, whereas pg for me was exhausting along with having a permanent hangover, IYKWIM.
Also, I thought I'd want to be back at work and bored at home. First 6 weeks I was too tired to think about it. By the time he was 6 months I really struggled to leave him. They smile, laugh and make it so clear, so early that you are the most perfect person in their world. One thing people told me before DS was born that is true is that you will wonder what on earth you did with your time before children!
Yes to clubs. IMHO you NEED other mums in your area with similar aged kids to stop you going bonkers, or at least I did. Swimming, music classes, baby massage all good. Sure start centre is a good place to start if unsure. My best days were popping over to another mums house and both of us sat feeding, chatting and eating cake!
Going back to work was hard, and TBH I have never felt as ambitious since returning (9/10 part time). Working mums always struggle with never feeling like the perfect employee or the perfect mum, but fortunately my DS doesn't need perfect!
Having my DS was the most amazing thing I've ever done. He is my world. And you do forget the horrid pregnancy. Only reason I have remembered so vividly now how dreadful it was is because I'm busy doing it again. Short term pain, long term phenomenal gain.
Sorry for mammoth post but wanted to tell you it's worth it and you'll be ok. Very best of luck.