The good part about public speaking while shy, and i speak from experience, is that the stomach churning and hand shaking tend to decrease, if not disapear, after 5-10 minutes. Even then, you can focus on your subject and your audience to avoid thinking about how terrified you are. And practice does help. There is a very thin line between feeling nervous and feeling anticipation. In time you may switch over. You will probably never be a showy preacher, but you can be a good one.
And the usual, practice by yourself, out loud, standing in front of an ambo or something similar, until you are fairly comfortable. Then get some friends to make you more nervous, and practice working through the nerves. And when its the real deal, the congregation all have cabbages for heads.