I don't know about the dyspraxia, but as Angela suggested, I was often pegged as "having an accent" because my parents are from different parts of the world. Plus, since I'm pretty in tune with the sounds of speech around me, I often have to struggle not to imitate the accents of the people to whom I am speaking. Add to that all the years of diction training from college, and I could sound like any number of people, depending on the situation. lol Besides that, there may be someone important in your life whom you unconsciously imitate in your speech patterns who speaks a little differently.

Many times, it's the vowels that are different more than anything else. And if they can't peg it, it probably isn't that much of a difference, just a slight difference in the way your speaking apparatus is made. If you don't have any difficulties with forming your vowels and such, I'd be surprised if it were actually dyspraxia. Then again, I'm not an expert, just an enthusiast.