The Apostle Paul had rather impressive credentials. He was extremely well-educated, well-connected, well-read, and well-traveled. A man of letters, Paul could speak with power and write effectively. He had status and prestige, and God used him to do amazing things.
The Apostle Peter did not have the same qualifications. He was a relatively uneducated, unconnected fisherman from the sticks. A man of action, Peter was constantly ready to jump the gun and often had to be held back. He had neither status nor prestige, yet he was used to accomplish equally amazing things.
A glimpse of these men before their conversions tells a similar story: both men had separate but equally-long rows to hoe in terms of submitting their wills and allowing God to redeem both their strengths and their weaknesses for his service.
The point here is that it doesn't matter so much who you are when you first meet Christ. What matters is what you allow to happen in you and through you after the Spirit gets hold of you.
Rich or poor, Ivy-league or GED, introvert or extrovert, white or blue collar: the ground is level when it comes to real effectiveness in God's service.
So stop worrying about who you are -- about how much education you have or don't have, about how your qualifications measure up to other Christians, or about whether or not your spiritual gift is currently seen as the most flashy.
Worry instead about the fact that all Christians have been called to be ministers of the Gospel.
The Pauls, the Peters, and everyone in between.
Take some time to re-calibrate. Start by putting your face in the Word, asking God to tune your heart, and getting your mind off your perceived shortcomings.
And yes, if the Spirit points out a weakness, ask for his help to fix it. If he calls you to more specific training, by all means heed that call. While it's true that quite a lot happened between the time that Jesus said to Peter, "Follow me," and Peter's first public sermon at Pentecost, it's also true that the road to Pentecost did not include Peter sitting at home in the his boat, waiting to feel "ready" to serve.
The time has come to stop worrying about who you are. Stop waiting to feel "ready," whatever that may mean. Instead, do what you can, when you can, where you can.
Remember that right now, you have a specific sphere of influence that no one else has. You rub shoulders every day with people whom no pastor or career missionary will ever meet.
You are you for a reason.
You are where you are for a reason.
Don't wait for God to send someone else "better qualified" to reach your friends, family, and neighbors.
He's already sent you.