First hiv test came back negative how many more do i take for a definite negative?

Which type of test: was it and how long after the high risk behavior was it done? About 97% of people will have enough antibodies to test positive on Antibody tests ("Rapid" tests) by the 12 week point.

Depends on timing: It depends on the particular test (or combination of tests) done and how long since last possible exopsure. The DUO test (HIV antibody plus p24 antigen) is conclusive any time 4 weeks or more after exposure. Most antibody-only tests ("third generation" tests) 6-8 weeks, even though official advice says to wait 3 months. Older antibody tests and the rapid oral fluids test still require 3 months.