Honestly, I still have a HUGE fear of speaking.
Trouble sleeping, stomach aches, trembling -- the full deal! Sometimes I wonder why I do it :)
I only started speaking because I wanted to recruit people to join my team at my last company. And I wanted it badly enough to speak publicly, despite it being one of my biggest fears.
In that sense, I think you have to find your "Why?" :)
Or, just apply to a bunch of conferences and once you get accepted, just say "Yes" and then figure it out somehow.
That could be what pushes you to do it the first time. Then you'll be hooked :)