If i'm 4 months n 1 week when did i actually get pregnant?

You tell us: You did not provide enough data to give you a valid answer. But, that is irrelevant in the era of the internet. You have all the tools you need at your fingertips to answer any question about your pregnancy. You may be surprised to learn that your answer can come from a simple conception calculator. I recommend this one: http://www.babymed.com/conception-calculator