Your Calling is not necessarily a career.
A few important points I'd like to clarify about identifying your life purpose:
Healing: Loosely Defined
Define heal in the broadest possible context. Healing is not limited to medical, clinical, scientific, or purely physical professions. Healing power is not limited in the form or media you choose as its vehicle or vessel.
I only very recently discovered that Words heal. This may seem obvious, given the professions of teaching, preaching, and counseling, but it is so much easier to see the content and context of other people's lives than it is to identify our own grace and power. For someone whose life theme revolves around writing and speaking, and who has spent these gifts primarily as a diarist and a writer of fiction for most of his life, the concept that words heal - that my words heal - was an absolute epiphany.
Your life purpose is not a job.
Do not confuse your mission in life with a job or a single, organized and defined profession or industry.
You life theme, your mission, your gifts, your passions are the things that always come through you, sometimes in spite of the job you do. Your purpose is the unique collection of Stuff you bring to any situation or circumstance. You actually don't have to try to pull out and execute your mission - it finds you. People feel it and respond to it, even when you are ignoring it, hiding it, or just not conscious of it.
Whatever It is, you're already doing it.
Your life purpose is not One Thing.
Your mission, your reason for being Here, is a synthesis and a synergy of everything you already are. Even the things that break your heart - even the things you hate about yourself or consider flaws - they are all ingredients in a unique recipe that is You.
Feel like you can't see the forest for the trees?
Does identifying your life purpose feel like you're looking for the perfect tree, considering each tree individually, and trying to decide which one is the right one to climb?
No one tree seems to be It, does it? You feel like you could spend your whole life trying out each tree, and you're afraid of wasting time, only to keep discovering
"That's not it... That wasn't the right one either... This one looks perfect, but the last time I thought that, it snapped like a twig..."
Back up, Goldilocks - there is no perfect bowl of porridge, there is no just right bed for you to find, there is no one tree to build your forthouse in...
Jobs may be individual trees, relationships may be too - You can't see the forest for the trees, and what you may not realize is that You are The Forest.
The whole danged wood is yours to name, claim, and explore.
If you're looking to go with the Flow, then maybe a watery metaphor will better serve you.
Rumi wrote one of my all time favorite mantras to this effect: