You say that you're a moral person and do not need God to tell you right from wrong. That isn't really what we need God for. Each of us has a conscience, so in that sense, you are right. Our problem comes in when we do things we know are not right. Like for example, have you ever told a lie? Do you like to be lied to? So then you do know it's not a great thing to do. You keep it hidden in secret because you know it to be wrong.
So why do people need God? Living a lie isn't much better than telling a lie. To be in concord with the truth, you should know for what purpose you were created. You should know who you are. You should know what you ought to be doing.
If you were created with a certain purpose in mind, how can you fulfill that purpose if you don't even know what it is.
There's a lot of things I like about Ayn Rand. One is that you should live life in accord with human nature. But when you deny God, you deny the truth about human nature. The following are truths you should know to live in accord with your nature.
* God created the world and mankind.
*Man was created with a purpose: to glorify God.
* Man was given the ability to choose, good or evil.
* Man chose to do evil
* As a result, God cursed mankind with death.
* All men with one exception inherited a nature inclined to evil. (Note, you're not the one exception. Neither am I.)
* This evil, otherwise known as sin, separated men from God, their creator.
* Men cannot fulfill their purpose while separated from God.
* God healed this separation by being born and living as a man--Jesus Christ, the messiah. The death penalty we earned by our sins was paid for when Jesus stepped in and died instead of us. He was resurrected 3 days after his death -- indicating that God the Father had accepted his sacrifice in our place. Now men are able to live together with God again and fulfill the purpose He has for us. The curse of death is broken when we own up to our sins and put our trust in Jesus.
Another thing I like about Ayn Rand is that she says men are by nature rational beings. This is true. God created us with a mind and expects us to use it. Acts 17:11 says, "Now the Bereans were more noble-minded than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if these teachings were true." God expects us to use our brains and figure out what is true or not.
There have been a lot of skeptics who, setting out to prove the Bible wrong, instead became convinced of its truth. Look at William Ramsay the archaeologist, J. Warner Wallace the cold case detective, Josh Mcdowell the law student, Hugh Ross the astrophysicist, Francis Collins the geneticist and many more. Take a look at their research about the Bible and God, or better yet, get the Bible and consider the evidence yourself.