Hey i am 17 and now after 3 months i will be 18 my height 5.11 and i wnt 2 reduce my height,how can i do so?

hey i am 17 and now after 3 months i will be 18 my height is 5.11 but sometimes it becomes 5.11 1/2 or sometimes 5.10 1/2 ,3 months ago i have joined gym to stop my height will it help me,my height increased due to cycling, i hate growing & want 2 stop or reduce my height,every one at home are short then me my dad is 5.8,i also started drinking 2 cups of coffee a day from2 weeks ago ,please tell me all this working out will help me to stop my height?is there any way 4 me 2 reduce my height abut 2-3 inches pls hel me!pls