That's exactly what I was going to say. A lot of men can get nervous that they won't be able to get their wife pregnant when TTC, or just plain performance anxiety! When we are TTC us women are usually eating, sleeping, and breathing TTC, and doing everything we can to make a perfect environment for a baby to implant.. that just leaves it up to DH to perform! That's a lot of pressure!
I am sure your DH wants to be involved with your TTC journey, but maybe if you took a "break" from talking to him about it, it may help? I mean, he'll still know you are TTC, but maybe if he doesn't know all the details about your CD, CM, temp, meds, etc.. he will be able to relax a bit, and just enjoy sex for sex.