There's a Christian cliche: God doesn't call the qualified, He qualifies the called. Nowhere is this seen more clearly than in the story of David and Goliath. Goliath, a 9ft tall war hero, was not defeated by a dedicated squad, or by a war machine, or even by another giant. Rather, his demise came at the hands of a young shepherd boy, so scrawny that even his own brothers scoffed at him as "just here to watch the battle".
I'm not here to tell you what you are called for, or even how you will know. But this much I do know: Whatever you are called for, you will succeed. By the power of God, whatever you were called for will be done, and you need not concern yourself with the size of the task, your personal qualifications to perform it, or those who mock you for trying. If you're doing the Lord's work, God Himself is doing His work through you.