Hi Greenstripes
I hope my post is of more help to you.
My 2 cents worth: as you are 40 (I am a good 5 years older than you), I think you need to make a decision. There is still time for you to have a child. You either try one way or another to have a child, or you make a decision that you will not be having a child.
If you make a clear decision about this then I think you will feel a bit better about it. And (as you have posted that you feel very sad about not having had a child so far in your life) if you decide or know in your heart that you absolutely want to have a baby, I think you should try.
I was fortunate and had children in my 30s. My sisters (for various reasons) were in your position a few years ago.
My elder sister who was very keen to have a baby in her 30s, made a conscious decision when she turned 40 that she no longer wanted children. She is single, developed a long term health condition that would prevent a healthy pregnancy in her late 30s. She considers herself 'child free'. A few years on she has developed a small circle of friends (male and female) who are also without children. I think she is at peace with her choice.
My younger sister (also single) and far less well off than the elder one, decided that she wanted to have a child. She has good health. She had never had a relationship and was very brave. She went down the donor sperm (from the US) and IVF route. It was expensive. It worked first try.
Although she is now a mother and her child is healthy and so on, it's not all rosy - after the baby was born the sheer amount of work, the need to respond to his endless waking up etc - she could not cope and she moved back into our family home and lives with our mother. Four years on and she now works 4 days a week and it is getting easier.
I do not know how the medical system works for you (here in Oz you need to pay for sperm and the US won't send sperm to your house - you have to use an IVF clinic but quite a bit is paid for through Medicare) but unless your health prevents you from carrying a child, there is no reason why you cannot decide to have a child and give it a try. 40 is not too old.
And now I think of it, over 10 years ago my cousin in north Europe had an IVF baby when she was over 40 - she also used donor sperm and was (and remained) single. She has no family help but I think there is a good system to assist parents in her country.
I understand your sadness, but you might overcome it by making a firm decision.