I just cant go on knowing im never going to be with him?

im in love with my best friend im 24 and hes not in love with me every day its so so painfull but he makes me so so so happy he lights my soul up we get along and laugh all day but i cant do it any more but i cant let go i really cant wen i think about leaving him it last about an hour and i miss him too much and wen i think about life with out him i just wana get a gun and put it to my head i dont no what to do