Always the one to initiate sex.

My husband and I have been living together for 4 almost 5 years. We've been married for a year and a half. We have a good marriage. We love each other through the good times and the bad-- but we are human and his Scottish temperament and my Irish stubbornness do allow us to bicker. Right now my husband wants to leave all of the TTC up to God and he is terrified I will turn into our neighbor (who won't even let her husband take a hot shower because it may damage his sperm). I've been pretty laid back about TTC. We have been TTC for 4 months.  I have PCOS and so I take the occasional OPK and measure my BBT.  But I'm so frustrated because every time I try and initiate sex he's 80% of the time he's tired or irritated and not in the mood. And it's not like sex has become a chore... It's usually just on the weekends that I even attempt because we are both so tired during the week. I'm just so frustrated because I know he loves me but sometimes I just want throw me up against the wall and make me feel wanted sex! Am I alone?? My husband is super work oriented and a totally type A. He's not cheating because it's not who he is and I know his soul. Just lacking romance and a sexual desire. Could it be age?? I'm 28 and he's 31 so I didn't think so but I'm just at a loss... Any inspiration to get him back in the groove?