Here is one suggestion:
Run to a bookstore, and pick up a copy of "Misquoting Jesus", by Bart Ehrman. The basic idea of the book is:
(1) there are no original writings of the New Testament--the earliest manuscripts come from the 2nd, 3rd, 4th centuries, or later, depending on the book.
(2) In the manuscripts that do exist, there are literally thousands and thousands of copying errors / discrepancies (no Xerox machines back then). The majority of these errors are insignificant, but there are still dozens, or even hundreds, that can significantly alter doctrine or belief.
(3) Given that there are all these errors we know about, how can we have confidence that the original writings, done by the hand of Paul, Luke, etc., are the same as the copies we do have, which were written from copies of copies of copies of copies of copies of copies stretching back 100 - 300 years?
(4) And if your faith is based solely on the Bible (sola scriptura, as the JWs are), how can you have such a strong faith if you can't even be sure of what the original writers wrote?