tea - I’m so sorry to read this. Loneliness as you describe must be terrifying.
However, I think it’s been hard for people to engage and give you meaningful advice because you have given such minimal info. For instance, what is the rest of your week like? Do you have a fulfilling job? What is your relationship history? You say you have lost important people, but who and when?
Also, I totally understand that approaching 40 is particularly difficult for women who are not childfree by choice. But you are hardly old fgs!! I’m in my 40s. When you are 49, you will look back and realise how ridiculous you sound. Age is always relative. The way I look at it is like this - I will never again be as young as I am today.
You know it is possible to feel lonely within a marriage? Or if you are depressed, to even feel cut off from your children? Again, I’m not saying these situations are directly comparable to yours, but nothing in life is fixed in stone.
You say internet dating is not for you, but nothing about why you feel this way? I imagine it is hideous tbh, but what have you got to lose? I know quite a few people who have met their partners at your age and had kids in their early 40s. I doubt they are any different to you.
When people start posting this kind of thing on MN, I always think they could do better with some therapy. Have you tried this?
Good luck 