@Amanda87 it's such a difficult one because you need him to be relaxed and in the mood, however your feelings of frustration are valid.
My advice, remember it's his experience too. IMO you're going to have to bend on this one, because he needs to feel supported and not pressured in order to do what he needs to do ;-)
Have you tried not making it about TTC? We found ourselves in a similar position after a couple of months trying, and honestly the issue can get worse if there's this elephant in the room all the time around his performance. Personally, I approached the issue with empathy and chose to remove as much pressure as I could. I stopped talking to him all the time about fertile days and OPKs, and just communicated to him that "what happens happens this month, let's just see". Obviously I was making sure the couple of times we did it were well within the window. After a month or two he began to feel less stressed about the whole situation and started to bring it up himself "aren't you ovulating soon?" etc. We also switched to morning times, as that was guaranteed to not succumb to the same issues. I appreciate all men aren't the same, but it worked for us.
It was his idea to get more strategic around TTC and told me that we should DTD every other day during my fertile window to make sure. We're now 22 weeks pregnant!
Outside stresses are tough, have you sat him down and listened to what's on his mind? Perhaps he just needs to feel heard and know you're in his corner (not saying you're not, of course). Maybe making a plan of all the things you need to do around the house, not-related to babies or TTC, might help him see the wood for the trees a little bit.
Go well and I do hope you guys find your rhythm again soon :-)