I'm a recently recovered stutterer who had high ambitions, so I understand your pain. A lot of people are recommending for you not to quit, but if your responsibilities cause you stress and anxiety, there's nothing to be ashamed about wanting a different job. It sounds like you have IT skills. Instead of looking at general labor jobs, have you tried looking for jobs that need your technical skills, but are more work focused on doing work that selling? I think you need to keep your confidence high while addressing your speech issues. Good luck!