Happily pregnant

My lover and i had a miscarriage back in March and ever since then baby fever has hit us straight in the face. We decided to not protect against pregnancy and see what happens. We just found out yesterday we are expecting and have never been more happy. But were also terrified to lose him or her.. Is there anything we can do to prevent or stop a miscarriage?? How do i get past the first trimester without freaking out over every little aspect??