For what it's worth, I don't think this is an uncommon problem - you're by no means alone in this. A few thoughts:
Learn to see the humour in everything. Some of the time, you're going to get up there to give a talk and everything's going to go wrong - you're going to trip over the power cord, your demo's going to fail, you'll have forgotten what you're going to say, some angry-looking professor in the front row will start heckling you, etc. You can't fully control these things; all you can control is how you react, and that only to some extent. In this situation, you've turned up to give the perfect version of an important talk, and at least to some extent, it hasn't gone well - you know it, the audience knows it. The job, to be blunt, is in no way a good'n'. Moreover, they're now all sitting there wondering what you're going to do. This is the perfect time to show them that you're self-aware and that you don't take yourself too seriously - crack a self-deprecating joke, make a humorous comment, or enthusiastically launch into telling them something interesting. Essentially, there's a lot of truth in this:
Leave yourself room to improvise. It's common to want to plan an important talk within an inch of its life, to make sure that you know exactly what you're going to say. Unfortunately, this can stress you out trying to remember what to say next, and make you sound stilted. I would argue that it's better not to plan the actual talk too much: instead, practise improvising. That way, when the inevitable problems arise, or people interrupt you, you'll know what to do. It's fine to have a rough plan, but be prepared to adapt it to the circumstances on the ground.
Publicly acknowledge your weaknesses and work on them. If presentations scare you, admit it - tell everyone, and ask them to give you lots of opportunities to present to help you get over it. Chances are, the people around you already know what your weaknesses are; by acknowledging them yourself, you neutralise them. Instead of being the person who's scared of presentations, you become the self-aware person who's scared of presentations but is dealing with it, which is a much better position to be in. The goal is to make the issue so intensely dull that no-one besides you will want to waste any time caring about it.
Detach your ego from your work. The aim of your talk is to tell other people something at least somewhat interesting and to help advance the field. You're there as a humble contributor to the great wall of human knowledge. You're not there to defend your work, except in so far as to make sure that other people gain a correct and fair understanding of it, and how it fits into the rest of the field. You're definitely not there to defend yourself - ultimately, you're just a curious person trying to help the field advance. If people have a problem with your work, help to focus the discussion on the evidence, and be prepared to agree with them if you're wrong. By avoiding the temptation to feel defensive about yourself or your work, you make yourself more relaxed, and better able to respond to input.
Finally: If you can, try to make the idea that anyone would want to focus on you rather than the field at hand seem ridiculous. As a speaker and as a researcher, you're human and flawed: you should know it, and you shouldn't be afraid to let them know it if the situation demands it. The point is that despite those flaws, you've turned up to do your best to make a contribution to the field. People who care about the field will respect that, and the rest don't matter.