"am wondering if self employment tax is calculated on gross income or gross income less self employment heath insurance deduction being I pay 100% of my premiums."
The amount paid for self-employed health insurance is a deduction on Schedule 1, not a business expense that is reportable on Schedule C. Because it is not reportable on Schedule C, the amount that you pay for self-employed health insurance does not reduce the net profit on which self-employment tax is determined.
