Still ttc our rainbow

Liza • 👦🏻 5/5/16 👼 8/13/18 🌈 👶🏻 12/15/19 👧 12/4/2019 (our 🌈 baby came early) 🤰with baby number 3

So, we are still trying- any ideas on using preseed- we never used it before when getting pregnant with our now 2 and 1/2 year old son. Really weird question, how does it help fertility?