What you're feeling isn't uncommon. There are countless professionals going through the same turmoil and trapping themselves in their thought process.
Most would keep their thoughts to themselves for the fear of being judged. Kudos to you for reaching out and sharing your story.
BB has already shared several ideas for you to think about. Here are a few more.
Your anxiety (if it is not triggered by any medical condition) probably originates from the high-stakes game that the MBA journey entails. It's just your gut-feel telling you to be careful.
If the entire prospect of taking a big leap sounds intimidating, you don't have to push yourself.
Try out other smaller and less risky ideas to test the waters - like free / short courses, volunteering, trying out a small business independently.
That'll give you reason to be happy and something to look forward to, other than your 9 to 5 job.
Hope you find the answers you're looking for.
And do get the medical angle sorted out at the earliest, to ensure there isn't a bigger underlying issue.
Good luck, buddy!