PreSeed does it work or waste of money???

hey I'm looking to try preseed for the first time. Been working on baby#2 but nothing happen. My son would love to be a big brother and my hubby will love to have another child, but it still hasn't happen for us. I'm just looking for people who actually used preseed and got pregnant from it. I just want to know does it work, how long did it take to get pregnant, how much to use and any other info will be great.