well if you can't seem to focus try to lighten up the self stress, going over your material and having it down pat will probably help. If you know the material cold, It would be one less thing you'll have to worry about and you'll just be able to move through it. Regarding the stutter, I dont know how you feel about your speech, but have you considered doing a little advertising before you start. Something quick like, "I just wanted to let you know I have a stutter so you'll probably hear that some time during the presentation." Just something small to clear the air for yourself and/or the audience. Getting it out in the open from the start might take off some of the pressure. If you don't feel comfortable with that, just try your best to not focus too much on not stuttering, but instead on what you're saying. You're probably going to stutter anyway and your here to present your content, not speak with total fluency. Remember to pause and phrase when speaking. Don't let your panic get the best of you and try to rush out all your sentences. Good speakers speak with appropriate pace and take pauses to let their information sink in. Just remember that this is only going to last as long as you're up there so just focus on your content and you'll be just fine :)