My advice is gonna feel a bit meaningless but can you try to stutter as much as you can while talking to your co-workers. Because you are trying not to stutter which is hard to accomplish but when you push yourself to stutter every word you say it'll feel more relaxed because you'll stutter in your volition. Then you will have more confidence in your speech because you have already experienced the worst possible situation.It's not clear how it will work when you talk about it, but if you put it into practice, you'll see the difference.