Hmm my suggestion is to try and change that maybe don't chat online at all for a few days and try that to see if the results in person don't improve at least a little bit maybe!
Online "relationships" are fantasy. Sounds like you more like the thought of him .. than him.
Maybe spend more time in person with him and less online. If you continue to feel the same way .. probably time to tell him how you feel to see if you can "fix" it.