Don't know what your culture is like at work but my place has been really accommodating with making sure I'm comfortable at meetings and get a proper hearing. Raise it to your manager and if they're worth their pay cheque they'll discuss ways to take some of that stress and self-hatred out of meetings. Plus stammering counts as a disability so depending on what country you're in there's a certain degree of responsibility for your company to make reasonable adjustments. I still hate going to meetings, but I'm at least confident that I won't just be thrown to the wolves or talked over if I start blocking - and that might help relax some of the tension / anticipation that contributes to it.