I think that being a mom as your primary identity and passion should not be something that you pursue for the rest of your life--otherwise you run the risk of turning in to a MIL from hades and perhaps becoming way too dependent on your adult children to make you happy.
But this is not the rest of your life, it's now. If it works for everyone now, then why not simply enjoy the now?
Honestly though, I suspect that perhaps you DO have a bit of fear in focusing on you or something other than your kids, if it's true that your relationship isn't what it could be now and because you mention that "is it fear". I know I was scared as hell to look at myself, and intense parenthood made it easy-peasy for me to not sit with myself. I'm far more comfortable running around being busy than I am trying new things out--for me. I really think that most moms go through a stage (or three or four) of that, it's pretty natural.
Last year, with all my kids in school all day for the first time, I pushed myself into taking a class that I'd wanted to take since I was a kid but never had time too--pottery (how stereotypical is that?). I love it, and took 3 more classes after that and will be taking my 4th - 8th this year.
For once in my parenting life I did something FOR ME that had *nothing* to do with family. To be honest, I think "going back to school" is for the family, not you, if it's in the context of "so I can support myself". I hated it when people asked me if I was going to go back to school, yuck. But believe it or not, I am actually considering one day pursuing a fine arts degree--I never thought of myself as an artist, and I don't really need the degree, but I might as well get something for taking all the classes I want to take. Not that a fine arts degree--I am in no way interested at all in teaching--would allow me to support myself anyway.
Anyway, I felt guilty for the first two classes, I mean really how dare I saddle my DH with our children and neglect them all for 3 hours every week so I could play with dirt? But it started to feel wonderful.
It's nice to have a hobby that is mine, that feeds my senses, where I can play with things that I can't have around the kids (like cool chemicals and FIRE!), and to be in a situation where I can be justme, and not my relationship stamped on my forehead. Nobody cares whose mom I am when I'm bent over the wheel or plunging a ceramic pot that's 1800 degrees into combustible materials to make it beautiful--I just get to be the hand shaping the clay and part of a team safely making art.
Didn't realize how important that was to me until I actually did it. Just this little bit is enough though...for now.