Prenatal vitamins while TTC

Just gathering input. .. glow suggests and some doctors say to make sure you're taking PN vitamins everyday while ttc. Is this the step I'm missing that's keeping us from getting a BFP each month or is it just kind of to get your body used to the vitamins for when the time comes? I'm hoping it isn't the magic pill I've needed to take to ensure a bean sticks or i would've been doing it all this time. It's hit or miss some months that i take them! Thoughts, previous experience stories, etc please! Thanks!