So sorry you're going through this, and need to have a self-imposed isolation. I work from home as well, and I find the isolation hard. I can imagine that feeling stuck with no way out will make it much, much harder.
When I'm going through something I find hard to bear, I find that planning a way out really helps: it can be something I'm unlikely to do, but it's important that I actually believe that I can if I need to.
How about if you put together a 'taxi-fund' with enough money for 5 or 6 trips - in a separate jar, somewhere within reach - which you know you can use if you need to. And tell yourself that if you need to top it up, then you will. You'll probably find that you don't need to use all of it (and then you'll have that extra money available for a treat when the baby arrives!) - but giving yourself permission up-front will help stop the anxiety.
From your name, I'm guessing you like baking. Tea and cakes would be a good bribe to get your friends to come and visit you! Even the ones who don't have a car could get a taxi (a few could come together, and share one if money's tight - if you're providing tea and cakes I think that's reasonable). Don't feel that you can't tell them that you could really use the company.
Since your DH gets home so early, make sure you do get out of the house together. Personally, I find that the worst thing about isolation is being within the same 4 walls all the time - you start to feel that you're not part of the real world! So, getting out is worth-while even if you're not going to be seeing friends: just drive into town, and go for a cup of coffee with your husband, or go to the library together, or whatever you would normally do by yourself now.
And similarly, make sure you get out of the house every day the weather is ok: go for a lunchtime walk, even if you've got no-where to go! It makes a huge difference.
Hopefully you'll find that even if you have to stop driving, it won't be as bad as you fear.