Most Helpful Guy
This is about work and nothing personal about you or the relationship. Working long hours can be all consuming. You just want to get off work, relax a little and go to bed. It can be extremely straining on a relationship.
If it's only for a couple of months you can just wait it out. Don't put him under any pressure to give you more time, he has enough pressure already. I don't know how many hours he's working but people can get very irritable and blow up at the slightest things. Pressure from you might cause him to blow and say things he doesn't mean.
I've been in companies where everyone was so stressed out that we had to be careful about everything we said, and we had to just ignore other people when their tempers blew. One time I just walked up to a guy's cube and tapped on the door, and he just blew up at me. He had his back to me and didn't even know who I was or what I wanted. You just have to let it go and try not to blow up back.
To give an idea how bad it can get, I've been in companies where I literally hated wasting the time to go to the bathroom.
I don't know about the rest of your relationship, but the work part is definitely not about you.
One thing you might try. He'll still be taking lunch breaks, so you might try asking if he wants to meet for a quick lunch somewhere. (he might also work while eating)
Just give him a lot of space and have patience. And don't be surprised if it lasts longer than 2 months.