I've found that using a little lube every time just adds to the experience (whether or not it's needed).
I've nothing more to add to the check your diet, make sure you're getting plenty of water, and to be on the safe side, talk to your gyno advice. But, at least go and have your mind put at ease.
Storm Berlin:I've noticed the lack of lubrication when using the vibe, too. Could it be that we just don't take the same amount of time for foreplay, which would normally get us wet, because we don't think it's necessary?