Kids finally in school, having a minor crisis

Youngest started kindergarten last month and oldest is now in 3rd grade. And now I have like 6 hours a day to myself. Sounds great right? Except I'm using it to sit in my car in parking lots feeling empty. I've been doing the stay-at-home dad thing for the past 5 years and my whole identity was tied up in that. Now I don't know who I am. Got a job lined up for next month but honestly I'm terrified. Anyone else experience identity crisis when your kids start school?