yeah, people are able to understand and I'm probably blocking for about a 2 seconds with the word umm. Say, for example, I'm saying the word imagine. I would draw it out and say it like "ummmagine" If I was talking to someone called Ian I would find myself saying "ummIan" I am using the "M" letter to soften up the hard sound of the vowel so I don't stutter but this has turned into blocking I guess you could say.