Damn, woman, that was profound. I spent way too many words trying to express what you captured in a few short words "Mother of an adult woman."
That your daughter is a woman, not a child, is your doing. You did that. You set the example and when your daughter was old enough to choose, it was you she chose to follow. Instead of doing life on someone's else's terms, she will do it her way, just like you did. Take a bow!
As soon as that son of yours reaches his age of maturity, you will be a free woman. On that note, I want to add some food for thought.
I cannot know, but you can, so let me put this out there. I have a sneaky hunch, your frustration with your ex-husband and his wife revolves around the same issue we've been discussing here. In a word, maturity. To be specific, I mean your maturity and their immaturity. Did you ever feel like screaming at them "grow the eff up"? Did it feel like they were play acting, just pretending to be adults? Did your mother-in-law infantilize her son so badly, he left a woman for a girl? Did you end up raising children with two other children? If so, that explains your emotional frazzle.
Quite frankly, teenagers are horrible human beings. Raising kids with a teenager would fray anyone. But maybe, that's the point . Maybe teenagers are so rotten, because parents need an incentive to shove them out of the nest.
My mother always said, you have to love your kids enough, to let them hate you. I think her words apply to your situation. Your mother-in-law clung to her son and he remained a child. You shoved your daughter out of the nest, and she turned into a woman.
Listen, you are fretting over a future rushing towards you very fast. A future when your nest will be empty, and you will be alone. Well, menopause will be over for you, before your son leaves home - and glory be; no more back of the mind worrying about periods, cramps and moods and pregnancy - that my dear is freedom!
Forget about dying alone. You can't live for your dying days. Making sure your dying days are not alone - what kind of life is that? No, no, no. That will not happen to you.
Are you mis-reading your emotions? Instead of anxiety, is that excitement that you feel? Excitement over all the possibilities life offers - beyond your son's 18th birthday? Instead of fear, is that guilt you feel? Guilt, because you can hardly wait for your son to grow up? Instead of frustration with your ex, is that impatience you feel? Impatience, because you can hardly tolerate one more conversation with your-boy-ex in a man's body?
Inventory those emotions and re-consider them - all of them. When your son leaves home, be careful you do not mistake a sense of peace and calm for depression. In fact, take a year or two and find the calm, indulge yourself, let it fill you up. If all you want to do is bake and garden, do it.
Now take a deep breath and get back to the business of growing up that son of yours. Your rewards waits on the other side of his 18th birthday.
