Are you a woman....or a man? That is the difference. If you are a man who wonders if he is TS then likely not. If you know....really know inside....you may be. A person who cd's and likes it and it helps them feel better temporarily, and then it makes them want more time as female, until they want to spend all their time female and are unhappy whenever they are male, they are very likely NOT a transsexual. It is knowing what you are not what you want to be.
It is like Arbon said as well, knowing you may have to give up everything in your life to make things right, and feeling like you must do it anyway.