Setting aside the internship for now, if you are currently a W-2 employee, you must be subject to social security (6.2%) and medicare (1.45%) withholding.
You might or might not have federal and state taxes withheld, depending on your wages, your family situation (children, spouse, etc.) and how you filled out the W-2.
How many dependents do you claim? Do you have a spouse, and do they work? Do you have social security and medicare withholding, or no withholding at all?
If you are being paid as an independent contractor, we may need to analyze the "on call" relationship in more details. Generally, if your employer controls your hours and working conditions, you are an employee and not a contractor.
