Well, I haven't gone through the exact same thing that you two are going through, but I can tell you that while my DW and I were ttc there were times when it was difficult. You get to the point where you're basically "scheduling" sex...between trying to keep up with her ovulation schedule and knowing when the best "window" of days was for us to have the best chance to conceive, etc. To top it all off, we found out a few months into ttc, that if you have sex more than once a day, you're hurting your chances of getting pregnant. ( maybe we were just naive, but neither one of us knew this...kind of bummed me out, because I was enjoying those days when we knew she was ovulating...LOL )
But after awhile, we both agreed that it makes it kind of hard, because it takes the spontaniety out of it, and then it almost feels like something you "have" to do, instead of something that you "want" to do. Don't get me wrong...I still looked forward to it every time, but it started to wear us both down after awhile.
We finally got to the point where we decided not to test to see if she was ovulating, and not to try to schedule it for the best days for conception, etc. We both decided we would just go back to living normally again and relax & just enjoy each other & our sex life. It took a lot of stress of off both of us, and made us both more relaxed...and not long after that, we found out that we were pregnant !! I really think it did help us to conceive, because we were more relaxed and not worrying so much about it. Stress can do a lot of funny things to your body, so it could definitely complicate the very delicate process of ttc.
It may be a combination of stress at work, along with worrying & stressing about ttc. It can be a very stressful time for both of you. The one bit of advice I can give, through personal experience, is to just try to relax and forget about everything else & enjoy each other. Schedule a date night or something like that, where the two of you can go out & have a good time, and just let everything happen naturally. I know that it definitely worked for us. Maybe if there's no "pressure" ( I use that word for lack of a better term ) to have sex, then he might find himself more in the mood for it, after all. KWIM ??
Anyway, I hope this helps you some and be sure to let us know how everything turns out. We'll be wishing you the best of luck !!!
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TxLady's DH & Hannah's Daddy
"That which does not kill us, only makes us stronger."
-Nietzsche
"It's not what lies behind us or before us that matters, but what lies within us."
-Mark Twain | 
