The first thing to do is define clearly what it means to be "fluent" or at least what it means for you (i.e. determine what level of proficiency you want to achieve and how you will measure that)
It may seems obvious but usually this is the hardest thing to do for someone learning a language. How i'm doing? What i need to improve? What i can do to improve? All stuff that comes as a consequence of defining a goal clearly.
So, even if you can't immerse yourself in a "native speaking environment", i suggest first and foremost to understand you current state for area of usage of the language:
- Can you understand spoken english/american english/fereigner english? Just watch some movie/tv show and you'll know the answer. With this you can also check your pronunciation.
- Does reading english text slow you down too much? Do you sometimes forget if you read something in eng or your native language? If yes this is a good sign imho.
- How is your vocabulary? Try reading different material, reading only IT oriented stuff is not enough and not indicative of how good your comprehension is, try reading books with completely different argument and see how it goes.
- Writing. Are you able to produce a good non technical short/long text? Do you notice errors in the paper/etc written by others?
- Speaking skill? Just register yourself to one of those language exchange sites and see hot it goes.
Once you identify where you are,what need to be improved and where you want to go (language-wise, e.g. speaking- being able to converse on the news of the day with a good english), just go on and check how it goes once in a while.
(40 days are not enough to evaluate anything, i'll suggest at least 3 months... seems more reasonable)