I live my life in constant fear of stress and conflict

I live my life in constant fear of stress and conflict The title explains it but it’s actually ruinous because I can’t do anything that puts me even slightly out of my comfort zone without fearing exposing myself and being viewed badly. My entire life, I have had many problems with speaking because I stutter. When I do speak fluently, I speak very slowly and I can’t always maintain the use of the correct tone for my words. People think I can’t even speak English properly and ask me where I am from. I can’t make my mouth adhere to what I actually want to say so I end up meandering and not properly articulating my thoughts or trailing off and giving up on the matter. Nowadays, I feel as if I mostly get by, avoiding speaking when possible or else trying to keep control of myself when I cannot. The problem is that whenever anything even slightly stressful occurs, particularly any situation where I have to be assertive or precise, I buckle under the pressure and immediately revert to my old ways. I can’t disagree with people or have opinions, and I have no desire to come into even the most small level of conflict with anybody because I know I will stutter. The scale of the problem is becoming somewhat comical because I have never gotten a hold of myself. To be honest, I’m not sure if this is common or uncommon, but, for me, stuttering is just the most prominent feature of some other problem that occurs whenever I get disturbed and lose my composure. My face twitches; sometimes, I even accidentally drool on myself. I feel as if my muscles have been coiled. My hands especially shake, my arms jerk inwards and my legs buckle under themselves so I get weird lurches if I don’t withdraw myself to somewhere private. It feels like somebody has heated up my brain and is pressing on me so I can’t control myself whereas, when I’m calm, it’s more like swaying, simmering water inside of my muscles. It’s really embarrassing. Again, I’m not sure whether this is common or uncommon, but I was raised with it clearly impressed upon me that whatever is wrong with me is shameful and that I am not normal and useless. My parents would call me rude things (like an idiot or a retard) incessantly, and still do. I spent my entire childhood being constantly harassed and bullied by everybody around me. I really do feel useless. It drives me to tears whenever I find myself in an unfavourable situation because it frustrates and embarrasses me so much. Even though I know that I’m not stupid, I can’t make my mouth or body comply so I just end up constantly portraying myself as awkward and off putting to other people. I can’t stand when somebody’s entire demeanour changes, and they instantly soften up and start to pity me, just because I can’t control myself. The worst thing is that I sometimes feel as if the issue has been largely resolved and then I get even slightly stressed or angered and realise that the only reason I felt that way was because I was avoiding any level of emotional disturbance so I wouldn’t expose myself in public. I don’t know how to build up my tolerance for this even though I spent years and years and years being taught how to hide the issue and speak more clearly. I think I wanted to post here because I can’t speak to anybody about this in person, for obvious reasons. Even when I mention that it frustrates me, people feel bad for me but dismiss it because they can’t understand just how much it constantly eats away at me inside.