Im not gaining weight!! :( HELP!?

Ok so I'm 13 about 74 lbs or 75 lbs & 4'11 . I'm so skiny!!!! Iwant to be thickerr ! Last year iwas 61 lbs and ijust want to gain atleast 10-15 in 1 or 2 months! No idont want muscle that looks disgusting on girls! And ieat a lot but inever gaint the weight pleasee help! What are good ways to gain weight without building muscle?