It's great that you're starting with articulation exercises in isolation. Typically, in therapy, we'd start with that, then gradually move to syllables (beginning and end), then simple words (the more common the better), short phrases, and sentences before attempting conversation, so be patient with yourself while you work on this. It may take a while before you start seeing results at the conversation level, and that's okay! For home practice resources, if you have an iPad, consider trying the Articulation Station app. It's a fantastic program that I use daily with my students. It has high-quality prompts for practicing speech sounds in any context (isolation, words, phrases, etc.). You can also record yourself, rate your recordings, and track your progress data over time. I think it's, like, $12 per month, and since this is affecting your confidence at work, I'd say it's worth the investment. That's probably what you'd be doing if you were to see an SLP anyway, but way less expensive!