Letty, in the nicest possible way, your post irritates me a bit. You talk as if you were a bit part in a rather boring play called 'your life'. Your function isn't just to enable everyone elses's life, you know, you can actually have a happy fulfilled life on your own (and it's a good role model to the children to realise that everyone's needs need to be met in a family).
You also have very low self-esteem, those words your child's friend spoke (which I very much don't think a child would say unless prompted massively, mine would never ever say anythink like that to me or about another friend's mum, they don't think in those terms) are essentially your view of yourself. You are not likely to be old and unattractive and odd, you are probably a normal looking mummy in her forties who, if she perhaps got some good counselling, could be a positive vibrant person with an interesting life.
Your relationship with your husband is dire, you live separate lives and he appears to avoid you entirely, but don't seem to want to talk about this. Counselling may help you work out what you want there as well.
Some of the suggestions on here on how to make friends/find a useful purpose in life have been great. I think they are a starting-point, but they aren't the whole story. I really think without examining how you came to be so passive in your own life, and not have your needs met at all in your relationship, and why you don't seem to make friends, you will just join stuff, have another quite lonely experience, and be back where you started.
Where do you see yourself in all of this? What's stopping you getting out there and making something of your life? Write a book, set up a business, be a company director, set up a charitable foundation. Aim high. Or take a part-time job to get out of the house and see where that leads. You sound clever but frustrated and need an outlet for that.
As someone else has said, it's great to meet new people, but more than that, you need a purpose which is satisfying to you. I hope you find it.