I'm not sure working with someone is the right approach - if you're this down on yourself about it right now you don't need anyone else telling you what's correct or incorrect - that will lead you down that slippery slope of low confidence.
I like the suggestion that tree had about reading out loud. I would take it a step further and record yourself and then listen back. John Fogerty of the Creedence Clearwater Revival did this to get the sound he wanted when he sang - he would record each performance, go home, and listen back, and then try different approaches until he found his groove. Start small - like 3-4 sentence passages. Painful as it will be the first few times, the good news is that nobody else needs to hear it other than you; pinpoint what you did or didn't like and then re-record it until you get the sound you want.
Honestly, though, don't let your self-consciousness about this hold you back from achieving your goals. Confidence, self-assurance, and security - no matter how feigned - go a really, really long way when dealing with NTs. I was reminded of this big-time today. One thing I'm really self-conscious about is that I like to explain everything, and what I intend to come across as caring and excitement and motivational usually ends up being long-winded and jampacked and pedantic (not to mention confusing and boring). I had to deliver a presentation for my job today; it was an orientation and I had to do two different sessions during the day. I made sure to plan and practice to keep it short - no longer than 5 minutes for 5 PPT slides. Looking at people's faces (including the department coordinator's) during that first session presentation I thought I was sunk, that people still found me boring and annoying, regardless of how concise I was. For session 2, I got there a little early, and the department coordinator, with a big smile and a chipper disposition, could not stop talking about how much she and the participants loved the goodies I had brought along with me to the orientation - goodies that included pens, key chains, and highlighters; this was, apparently, good enough for them to want me to present at other events for them. Long story short - they could have cared less how on-target and engaging the material was so long as it was accurate and I presented it with certainty. Ultimately, and ironically, the "useless" decorum was what made my presentation memorable and engaged them.
