for you OP.
I know I had some wobbles when pregnant, but you sound very depressed, overwhelmed and lonely.
I can't add to the great advice you have been given here. All is spot on.
One thing that does strike me though is that your DH and his job seem to be calling far too many of the shots here. This has contributed to your isolation, I am sure. Maybe it isn't intentional, but just badly thought out and one sided. You need to talk to him and see where that leads you.
Your commute is far too long and complicated. Whatever DH's situation, I think it is too much for you and if you want to return to work after having the baby (I did after DD1) you really need to address it.
That may to a large extent dictate where you can live in practical terms, but it really shouldn't be only DH's circumstances that dictate.
Is DH a farmer or something like that? Some of what you say leads me to think he may be (sheep and fields, property as part of the job forever, and the rural setting that means isolation if you don't drive). Some of my wider family are farmers and are very entrenched where they are, haven't moved in decades.
Were you a city dweller transplanted into this "rural idyll"? I think it can be a very difficult adjustment to make.You might get used to it and will have to give it a chance, but it isn't everyone's cup of tea and it is fine to admit that and to say that you want to be somewhere with more of a community, some facilities and some transport links.