If you have a problem with punctuation you should pay attention to it immediately. Like bad spelling, bad punctuation
(a) irritates the examiner,
(b) makes the essay harder to read and understand
(c) makes anyone who reads your work, now or at any later date in life, underestimate your intelligence, perhaps considerably.
I would recommend you do something about this. You don't have to (it's your life), but if you do, a good place to start is in the The Oxford Guide to Writing, which sets out the main punctuation rules in English very clearly and simply.