No, you can't be Head of Household if someone else is HOH in the same house. You also cannot be Head of Household if you are not the one paying for more than half of the home's costs, regardless of the filing status used by others.
Head of Household means you are not married, and paying more than 1/2 of the costs of the home your child resides in. Presumably, your parents are the ones paying for the costs of the home.
Click Edit next to Filing Status under Personal Info. Click Done on the page "Your children and others you support". Continue until you see the question, "Did you pay more than half the cost to keep up your home in 2016?" When you indicate "No", you will receive the Single status.
To change your filing status you need to amend your return.
Here's how you amend your return:
Amended return can't be e-file, you need to print it and mail it in.
To correct your filing status: