The Bible tells you the answer. There are many grounds on why God shouldn't have called you. But don't be troubled. You’re in good party. Moses stammered. David's armor didn't fit. John Mark was unwanted by Paul. Timothy had ulcers. Hosea's wife was a prostitute. Amos' only training was in the school of fig-tree snipping. Jacob was a liar. David had an issue. Solomon was too wealthy. Abraham was too mature (old if you don’t mind). David was too youthful (young if I may add). Peter was afraid of death (hello, aren’t we all?). Lazarus was dead. John was self-righteous (strict would be an understatement). Naomi was a widow. Paul was a murderer (so was Moses). Jonah ran from God. Miriam was a gossip (too friendly I guessed). Gideon and Thomas both doubted. Jeremiah was depressed and suicidal. Elijah was burned out. John the Baptist was a loudmouth. Martha was a worry-wart. Mary was lazy. Samson had long hair. Noah got drunk. Did I mention that Moses had a short fuse? (So did Peter, Paul--well, lots of folks did, I think you are too).
But God doesn't require a job interview. He doesn't hire and fire like most bosses, because He's more our Dad than our Boss. He doesn't look at fiscal gain or loss. He's not prejudiced or partial, not judging, resentful, impudent, or strident, not deaf to our cry, not blind to our need. As much as we try, God's gifts are free, open for all and at no cost. We could do wonderful things for wonderful people and still not be ...well, wonderful. Satan says, "You're not worthy." Jesus says, "So what? I AM." Satan looks back and sees our mistakes. God looks back and sees the cross. He doesn't calculate what you did in the past. It's not even on the record. Sure. There are lots of reasons why God shouldn't have called us. But if we are magically in love with Him, if we hunger for Him more than our next breath, He'll use us in spite of who we are, where we've been, or what we look like. I pray that as Christians, we will step out of our limitations into the illimitable nature of who God is. Then our passion for God and our passion to communicate with Him will make short work of our limitations.
To doubt, brings limitation to God’s limitless capacity, unbounded ability, and infinite knowledge.
The answer for that question? The answer should be obvious!!!!