Most of my students are mortified to hear that they have been mispronouncing words for years. Worse yet, is that no one corrected them.
In America, people think it is rude to tell you that you are pronouncing a word incorrectly. They do not want to offend you. At work, most people won’t say anything because they feel it may be considered a form of discrimination. The good news is that most people want to help. You just need to ask.
Tell a trusted colleague or friend that you need help. Ask him to tell you if you say a word incorrectly or if he doesn’t understand something that you say. Once a colleague has your permission, he will correct your speech and help you to improve your accent.