Why can't we get pregnant

Kayla • I`m 23 years old. I have had 6 open heart surgeries and I have a pacemaker. My fiancé and I are trying for our first.
We've been trying for almost 6 months and nothing is working. I need help! We are 22 and 23. We are starting to get our paternal and maternal instincts we don't want to wait but need helpful told from other. Please