it's one of the most common avoidance behavior (and to be honest, a lot of non-stutterers use it too). It's a poor habit and doesn't help you overcome your stuttering. I used to do it but I stopped. How I did it, I chose a couple of easy interactions each day and made my goal to not say um or uh at all. I kept this up a couple of time every day. Then i tried it out a couple times a day in slightly harder situations. Eventually the habit broke and was replaced with just moving straight to the stuttered sound instead of trying to dance around it. Makes my communication a lot more direct and less cluttered.