what can i do to find my dad

my name is alexus and i want to know how i can find my dad i dont know nothing about him i am 12 and i do not want to go enny longer with out knowing him i know if i do that will be all pain this is my story : i was my moms first kid and she did not make good choose with all her kids she has 4 all tilt none of them live with her they all live with there or my grandparents we do have a good life but they all know there dad if they lived with them for a little or just visited but some time i cry my self to sleep beaucks i dont know who mine is and when i ask they all tell me they dont know who he is but i think they do they dont want to tell me but they dont know how munch pain i am for not knowing all i know is that when i was a baby he would stop by to give me dippers or toys so he dose know i am in this world and i left out i was his first kid and my unkle know him but i dont see him alot to talk abut him all i know is that people call him j.p that it and he has 1 kid me and 3 step kids i want to be part of his life so what can i do