Husband won't have sex when we "need to"

I tell him the days I am ovulating and must have sex in order for us to have a better chance of getting pregnant. I just turned 37, and he is 44, neither of us have never had kids. We both want to have kids, but I feel like we should be trying harder, especially on the days I am ovulating. He has a weird work schedule so when he is home I am at work and vice versa. I am tired when I come home from work and we never seem to have sex in the afternoon on the weekends when I am normally the most sexual feeling. I just don't know what to do, how to talk about it, time is ticking, it needs to happen sooner than later!!