I personally don’t think that there would be any problem with you posting your story, though you must remember that alot of people here don’t have a great deal of patience with long posts. Reading pages and pages about someone else’s story is not always considered the most interesting material, especially for someone, like atheists, who are already predisposed to certain contrary opinions. Or, in short, we don’t like to hear people go on and on about themselves! Your best bet is to make it succint and to the point. Perhaps your leading sentence ought to be the realization that you came to which prompted your conversion, or, if your story were to be constructed like a logical proof, offer your readers the conclusion then tag on the premises.