referencing is such a pain, sometimes even academics get it wrong - i have spotted referencing errors in peer reviewed publications and manuscripts, so don't be too hard on yourself. that being said, it is one of the core marking criteria, so if they spot all the mistakes you have been able to spot (highly unlikely), they might take a tiny little mark out, or if they are understanding, which they should be, they might just mention in the feedback.
finally - stop reading stuff after you have submitted it, you will always find an error or two!! gd luck.