Are you in school? High school? College? During high school I avoided presentations at all costs, usually by doing alternative assignments or one-on-one presentations with teachers. In college I didn't want to skirt around the problem (and probably wouldn't have been able to even if I'd tried), and at a certain point I started feeling more confident based on successful presentations here and there. It took about two years of being terrified and, like you said, feeling awful afterward, so it's not like a magical switch went off or anything. Ultimately, I think student teaching had a hugely positive impact on my approach to presentations. Now I tend to think of myself as putting on an act. It helps to be over-the-top, it helps to be informal and funny, it helps to invite audience participation-- if and when any of those things are appropriate, of course. So whatever point you're at in life, my advice is that it will get better the more you do it. And the more successful presentations you have, the better you'll be able to pinpoint what made them successful and utilize those things in the future.