There are loads of other ways to share your knowledge. Maybe you want to try podcasting, blogging, vlogging, writing articles for relevant magazines/web sites?

Heck, you could even make funny songs to get your message out :-) As a speaker though, I feel at home on stage and the feedback has been positive over all the years, so I feel comfortable with being a speaker.

As always, do what you makes you feel good, don't force yourself into something you don't like. The audience will notice immediately and some audiences can be very hostile. Most of the time though they are very forgiving in my experience.