This is one of the things I found strange when I moved back to the UK - the lack of willingness of some British women to socialise and do anything away from their husband and children. (not to mention the obsession with their ages, vat an age where its perfectly normal to do things that they claim to be too old to things at).
It's well known that socialising outside a marriage and making new friends is good for your mental and physical health and stands you in good stead throughout your life.
Now, I know that in a British based discussion group, I'm going to he absolutely slated for this, but I honestly found your post so depressing. The comments about the pregnant woman, her age, the use of babyish phrases ("cos", "and I don't want to", "I am not bothered"), etc) , seriously, its perfectly normal to make new friends, you are allowed to have friends who are different ages to you, and many of us can't be bothered socialising but occasionally make the effort out of consideration for other people.
Why on earth would getting invited to things make you grumpy? So yes, you probably will get a reputation for being abti-social, your comments about them are pretty awful to read actually and 8 think I'd stop wanti g to run with you at all as you really do come across as quite unpleasant (although by the sound of it, that would please you).
Do you know what atrophying is?