Earlier this year an Australian academic produced a report claiming that verbal communication skills are the greatest barrier to non English speakers practicing in the area they are trained in.
In the workplaces of most corporations' IT and project departments in Australia there is a strongly multicultural workforce. People typically do not mind having to deal with thick accents and are happy to help their peers if they have particular challenges with the language. People, at a day to day human interaction level, generally want to help you do well. It's the hiring process that provides the biggest challenge.
And of course the best way to overcome your concerns about your communication skills are to (a) practice, and (b) realise that you are probably much better than you think.
Follow Larimar's advice and check out Toastmasters. The features they can provide are opportunities to practice public speaking, and will even video or tape your speaking - which is a great way to hear what you really sound like (and generally we all hate hearing ourselves the first time.)
Lastly; in the workplace; don't fear asking questions. It is your job and people will respect you if you ask. After all, it will be the unasked questions that cause the project to fail.