A "coward" is not something you "are" imo, social akwardness is part of the stuttering package, but its mostly just a vicious cycle that makes your stutter worse > makes you more anxious to speak > even more stuttering. What really helped me is actively pushing at the edge of my boundaries, for example i found the checkout at the store to be one of the scariest things in existence, as you slowly get closer and closer to the "danger" of having to speak,bonus points to make it 10x worse if i had to return something, especially if it wasn't mine(looking at you mom). So what i did was i bought a whole bunch of stuff i did not need at a lot of different stores(which did make a dent in my bank account) so i had to return them, if i wanted the money back; as a way to force myself. Since that day i was no longer scared of going to the checkout, as your mind has finally registered that it is actually not "dangerous"