Nitrofurantoin to prevent UTIs

For years i avoided sex because i got a UTI every single time, no matter who it was or what type of precautions i took (peeing, showering, protection, natural lubes, etc...) I finally was able to speak to a gyno that tooke seriously and she wrote me a prescription for nitrofurantoin to take after sex as a preventative measure. The problem is i havent had sex in over 4 years because of this issue and now im terrified to try again! How do i get back into it without constantly worrying that i'll get sick again???