i have problam in penis i get erection its weak tim only 21 and when i get erection when lying on back my penis lose erection in like a second and i can feel blood flowing down in that postion when im lying on back what this problam is its really scarey and i feel like im impotant in 21 plz help me i can feeel blow flowing losing in my penis but at night my erection is ok not too bad i cant feeel flowing at night and wehevet im horney my penis erect n very sof feel light weight aswll like there no hardenes plz. Someone answer me