The main characteristic of stuttering is not being able to say basic sound like a vowel sound or consonant sound at infrequent periods. If you notice that it's the first part of a word that you're getting stuck on or the first letter, then you probably have a stutter. The speaking fast could be a secondary behaviour you've developed to avoid getting stuck on words by trying to get as much words out as possible before you get stuck on a word. Try slowing down, like you're talking in slow motion and notice what sounds you're getting stuck on and identify a pattern. If you often have trouble saying your own name, then yea, you probably have a stutter since this is common for people for who stutter.