Midlife crisis?

I will be 49 in April. I'm old  I'm a Nana for heaven's sake!
There are so many things I wanted to do with my life.  I've seen and done so much more than I ever thought I would.
I've lived so much longer than they ever thought I would. than I ever thought I would  I'm on borrowed time, it would seem. 
Idk what I have to give. What greatness is in me? Idk. I doubt often my worth in this life . What am I doing to create greatness?
I talked to my shrink. She seems to think this is my "midlife crisis". Going back in my mind , looking around and being totally fed up with how little i have done. I raised my kids. Yes. I am proud of that. I am proud of them. But really, I spent their formative years in, what I thought , was my death bed. So did I raise them or did they raise themselves.  I'm forever proud of my girls.  But what else have I done?
I feel like I could have done so much more had I been healthy, mentally and physically. Could I have taught kids like I wanted ? Could I have sang like I truly wanted to in high school, and followed that dream? Damn i really thought I could have been a singer ! Then maybe a teacher? I had dreams once upon a time ago.
I can't blame everything on ph. I've never had the drive or umph to get out and go for my dreams. 

People like Sally  may she rest in peace , Chloe & Sean Wyman may he rest Peacefully, they went out & lived their dreams!! So many others are despite their diagnosis.

It's not to late for me to do something , i know. But what ?
These thoughts keep going round and round in my head. I'm able yo keep the negative self talk to a minimum, which is good, but how good is going back and taking stalk and not working to make my life better?
Can things really get better ? Idk. I don't know.