Hey Noctuary,
Your feelings are not uncommon, I suspect, even in people who have married and have children. I have both a wife and a son, and I'm about your age, and I still struggle with feelings of worthlessness at times. I feel like there is so much more I could have accomplished.

I am working on getting a degree and pursuing things that interest me just because they interest me.
I've been doing some research into certain people and also philosophical topics that interest me. I even hope to get published.