How do I start over at 29?

I have a commerce degree and a master of journalism, and have been working in marketing / communications for the past 7 years. I hate corporate life. It’s not for me. I always saw myself working in healthcare and pursuing something that meant ongoing study, research and engagement. I feel chronically understimulated, and it’s having an impact on my mental health. I’m at the point that I’d start from scratch and go back and study - I just don’t know what to do. I’m scared to commit to something else but I can’t imagine living my life like this until I retire. Where do I start?