This might be the worst part, and how do I get past it?

This might be the worst part, and how do I get past it? Been stuttering all my life. With alot of people I´m basicly 100% fluent, in other situations and with some people I stutter like crazy. The worst part is how the stuttering effects what I say, how I act, and what I´m able to think while trying to talk. For some reason I have a tendency to stutter more with people with authority (and people I dont know, and in situations with time preassure, and in loud places etc), and when I stutter I usualy look away (like many seem to do) and often look down. When I get blocks alot of mental energy goes to trying to get past the block, so I dont have much energy left to focus on what I wanted to say. That loss of focus makes harder to talk in a relaxed manner: I cant even come up with things to say, and if I can I still cant say the things like I want because of the stutter. So the things I say are choped up and simplified. That combined with the habit of looking away/down when I stutter and me not being very tall (like 172-173cm) make me feel like a child or socialy incompetent teen. This might be the worst part, the feeling that I cant be an adult on equal terms. SO how do I overcome this? I dont get this feeling when I can speak fluently. I´m glad I have people around with who I can be fluent, relaxed etc. It woul be real hard if I didnt get those boosts