help!!

HI! my name is Hailey, I'm 19, and am trying for #2 a little back ground, I was 15 when I had my first child due to a sexual assault, I made a concious decision to give my son up for adoption, to a worthy family to provide and take care of him, that had been ttc themselves but sadly found out where infertile.. now I'm engaged and trying with my soon to be husband but am having trouble my period will go missing sometimes two months in a row with added pregnancy symptoms but all to have my hope crushed by negative tests or af coming at last... how do i conceive when my period is bonkers? any advice helps. I had a C-section and have had a STD before but luckily caught it early and got rid of it.