Is what I have considered a stutter?

Is what I have considered a stutter? So I'm not sure if what I do is considered stuttering. Sometimes when I talk there are certain words that just dont come out. The words are never the same either. My brain knows the word I want to say, but I just physically cant say that particular word at that time. For example, I want to say something like: "You have a very well behaved dog", but I will just say, "You have a very well behaved ...." and my mouth just wont say dog. The way I have got around this is by substituting another word in its place after a few seconds of awkward silence. "You have a very well behaved .... puppy". Sometimes I have to completely restructure a sentence to get what I want to say out. Sometimes if I cant think of another way to say something after my silence I just say "nevermind". The funny thing is that usually I can say it at a later time just fine. So is this some form of a stutter?