TTC our first

We are TTC our first baby together. This is our 4th month trying and in getting a little discouraged. My fiancé has 2 beautiful children and we want to add 2 more to our family. Can anyone tell me if anything has helped them conceived. I have been taking prenatals and we are going to try preseed, as well as opks this month too. Just wishing it would happen already. Thanks in advance!