Eiepie...just wanted to say, you've just pretty much decribed my life, 3 children eldest being my dd who is 13 in 2 weeks, an 8 year ld ds and a 2 year old dd. I too am not invited along to anything with friends, they all have couples nights, I dont get invited. 
Playground thing too, I get ignored totally. Also I commented on my facebook about how shit my day had been the other day, no one responded, yet someone put on facebook how they have brought some new shoes and they had like 20 something comments???
Made me cry that did. I feel totally alone, been single nearly two years. I never get to go out cos I quite simply cant afford. I cant ever imagine a situation where I would ever meet anyone. I really dont want to go down the dating site road but I feel so bloody lonely. I have absolutely no one to talk too. 
I work part time but the staff where I work dont want to hear me winging, they are not friends, they are work colleagues, yes I have a laugh with them but thats as far as it goes.
Just fed up...I should change my name. 
I tried to write a really long post on this thread the other day, spent ten minutes writing everything I thought, went to post it and it failed and I lost the whole thing....typical for me that, needless to say that made me cry a little and laugh a little too at just how bloody shit things are at the moment that when i actually try to talk to other people who are feeling the same way, it goes tits up so to speak. 