Hi My Name Is John And I Was About To

Hi my name is John and I was about to have sex with a girl the day before I had a erection and when I was going to have sex with this girl my dick ain't standing up I try pumping it but I jus ejaculate and it went down back to day I was masturbating to see if it stand up and it did but only when I going to ejaculate it stand up hard watch can be the cause of that am scared I need the help pls