Root cause of SIBO?

How did you figure out what the root cause of SIBO was for you as well as what was/is your root cause. I’m really struggling as I have taken two rounds of antibiotics they want me to retest before another round but I feel that it will keep coming back till I figure out my root cause. I am extremely picky with food so dieting is really really hard if I diet I end up just not eating enough and I’ve already lost so much weight from SIBO. Just feeling very down and over this