negative gain in yagi antenna on microstrip

hi....everyone......i am trying to simulate yagi antenna at 5GHz using hfss ...but getting a negative gain.............please help me......please...please

Even a high-gain antenna as Yagi, can get negative gain if is not tuned on the right frequency, or other parameters of the antenna are not well designed.
You gave NO design information, but you ask for help.

here is the radiation pattern.....i dont know how to attatch the design

here is the parameters
substrate (70*100*1.6)mm
ground (70*38)mm
feed_length (38*4)mm+(7*3)mm
driven (56*5)mm
director (15*5)mm
operating frequency 5GHz