it is bloody hard! you just dont know - and nobody could explain, pre-baby how difficult it is. It gets easier as they get older - its still tiring when they are older, but as they grow you have a relationship with a real little person and that makes all the difference.
I know its not easy getting out on a winters day - but its not for the baby you are getting out its for you - dont bother with anything unless you enjoy it. My son didnt get anything out of baby groups until he was about 1 - but I had to go out and meet people.
Keep bag packed next to buggy and get a winter outfit you wear - look at the week ahead every weekend and make sure you have something to do every day - personally I find if I get out it only has to be once, and then the rest of the day is easier -
Presume you dont have an NCt group? I found really friendly people at NCT coffee morning, you dont have to be a member , look up your area - and hard as it is, make the effort to do it.
childrens centres - is there a BF support group if thats what you are doing? baby massage/ etc? there will be an under 1s drop in somewhere near, for when baby is a bit older.
do you have friends with babies you can invite over or meet in a pub/ cafe etc? at this age they are a lot easier to take around than a toddler in some ways - even if baby sleeps in the pram while you have a hot chocolate and read the paper - mornings are usually quite in cafes...
library for singing groups...
its exhausting - but sitting at home always made me feel more tired and crap - once you have had your daily outing, get a dvd on and just sit on the sofa!
personally next time round I will get dp to do a dream feed with a bottle at about 1030 pm so I can go to bed early - would that work for you?
also - if you are really sruggling, could you afford a bit of help at home - mothers help/ local woman who will come and cuddle the baby while you have a shower/ eat dinner? remember, women have never traditionally in human history done baby raising alone! its not meant to be like that.