Please share your worries with your midwife- they will have seen this many times before and should have policies in place to support you. You don't need to deal with this on your own and even though last time was very hard it doesn't need to be the same this time round.
I am actively avoiding other "mums" and "expectant mums" as i have little tolerance for competition and superficial aquantance. I do not have friends who are mummy friends, i have lifelong friends who i have had for ever. They all work, have kids (coincidentally) but my friendship with these folk are not based on the fact that we all have kids.
I would say that i am probably antisocial and that i will be making the lonliness/isolation worse. Currently, that's ok with me but i know it will be bad for my state of mind when the baby is here and DH is back at work.
I attribute some of my depressionw ith these people at play groups making me feel worthless and shit for just being there, so i wont be putting myself through that again.
I dont have family that would be interested in us either. Although they all live within a 5 minute drive from here, and i have a large family, they are not people i can just drop in on, or that will come anywhere near us.
I found it all went much faster the second time around even though my second child was harder than my first. I guess its because I was a bit more relaxed and with two children I couldn't focus solely on the baby, it had to fit in with my oldest (who was 4.5 and at school).
Second time around I was also much more aware of what was essential and what wasn't, plus I knew it wasn't going to last forever. So I pretty much just did basic housework, didn't go to every clinic and class, didn't beat myself up if I took the baby on the school run in pajamas. I didn't spend hours making purees but spent that time with the DC or giving myself some free time. I also don't go to many playgroups, DS didn't get much out of them until he was 12 months plus and I hated that awkward/competitive chatter.
We went out almost every day however, even if it was just to the library or shops and Dh and I discussed the above before DS was born. I had PND and PTSD after DD and we were both eager that I didn't put myself under too much stress. DS's birth was much much easier and I healed much faster the second time around which helped too. Taking the pressure off really helped me relax and enjoy my baby.
Talk talk talk. Don't let it be something you ignore as its too easy for it to get out of hand. And try not to over think things, Easier said than done I know. I hope it all goes well and you enjoy your bundle of squish!