I am fairly certain most people go through this stage. The "Hey, something is happening here..Whoa this is cool, and weird, and...." stage. Before ya know it your mind is racing, and you lose your cencentration. The only way I know of getting past this is with practice. Pre-exit sensations, especially at first, can be very intense. If I may offer a suggestion...the next time you decide to meditate accept that for that session, your goal will not be to have an OBE, but rather to become familiar and comfortable with the experience itself. When you start to experience the sensations of falling/expanding/tingling/snapping/crackling/popping, what have you...do your best to just ride it out, and know that you are experincing what many astral travelers have before you, and that it is perfectly natural.