What am I doing wrong?

So me and my fiancé have been trying to conceive (we have been together for six years) we've been trying for at least a year. We have both seen doctors and everything is normal but month after month of trying and I've come up empty. I have made a lot of life style changes including tracking my cycle. Seems like this is impossible. Does anyone have tips? (Besides the obvious tracking and what not) feel like giving up. :(