Just need some support.

My husband and I have a 6 year old daughter but have struggled to conceive again. We have never used birth control or done anything to prevent it, but it hasn't happened. I recently started tracking ovulation again and heard about preseed on here so I bought it. This is the first month we used it but I'm not sure if we used it too late or not. It was about half way through my fertile window. Has anyone tried it before? How/when did you use it and how long did it take if it worked? I've been discouraged for a long time now, I'm thinking maybe we can't have anymore.