Really just ready to be pregnant!

So, I feel like I could use some advise... But here is my story. At the end of my senior year I found out I was pregnant. This happened at a time when me and the father were not ready and between fights and worries there was a lot of stess in the beginning. We found out I miscarried 4 days after my first ultrasound. Since then I haven't been able to get it off my mind. But now I am with a man that I love very much. I am almost done with college, we both have decent jobs, and we are looking at houses. A few months ago we decided to really start trying to conceive, but honestly we have taken no steps to prevent pregnacy before this. So far there has there has been nothing... I worry I'm doing something wrong, or maybe that I can't become pregnant. He has 3 boys, so I know he can..