How can I be a preacher when I feel so awkward telling people about the lord?

I really would like to be a preacher and I pray that God will help me choose the right words to speak when I am spreading the gospel. He still has not answered my prayer however. I just feel really nervous when I tell people about Jesus and people laugh at me. I usually approach a person and say "hi there, my name is Denny and I am here to tell you about Jesus. He died for you on the cross 2,000 years ago to pay the price for our sins. You just have to believe in him in order to avoid being burnt in a lake of hellfire throughout eternity." Most of the time people laugh at me and I become visibly nervous and ask them politely to please stop laughing at me. Sometimes I get angry and tell them about how they deserve to burn in hell though that does not seem to make a difference either. I also dont know how to answer many questions atheist have for me when I dont have my bible around and find myself stuttering like a nervous train wreck. How can I be more effective? I feel like such a loser but I know that if I continue to pray hard enough the right words will just come magically from my mouth.