Relax and take a deep breath, you're not the only selectee to have found himself/herself in a similar situation. Your birth certificate should always have your father's name, since you were born to him before you got married, right?
. So, apply for a new birth certificate with your maiden (father's last name). As for the police clearance certificate, it should be in your current last name (husband's surname) since you're applying for the clearance certificate after your marriage. Don't forge documents or manipulate them, such lies will eventually catch up and backfire.
If you can, I suggest you do a formal change of name, so that you have an additional legal document for your new last name (in addition to your marriage certificate - it wouldn't hurt to have that), and if you can't don't panic. You may want to consider getting a new passport using the new last name too.
Also go ahead and email KCC with regards to your change of name. Remember though to always use the last name listed on your notification anytime you contact KCC.
All the best!