For a situation like this, I recommend looking into with your doctor a benzodiazepine and/or a beta blocker. I have them for college and they make a world of difference. The benzo will ease the mental stress and the beta blocker will ease the physical symptoms that go along, making the presentation doable with practice. I'm afraid there is no OTC medication I could say is worth trying, especially for a big presentation. Diet and exercise though is very important. Create a regime for yourself to work on these next few weeks. It should do your mind a lot of good. Especially on the day of the presentation, take a nice long run or do any sort of rigorous cardio exercise beforehand. There have been studies showing how exercise can reduce anxiety levels by nearly 50%. Practice a ton as well. Know your material inside-out and once you do, it'll raise your confidence level that extra step further.
If I can't be my own
I'd feel better dead