Sleep deprivation is destroying me

My 18-month-old has been waking up 3-4 times a night for months. My wife and I are taking turns but I'm on duty 4 nights a week and it's turning me into a zombie. I'm snapping at people at work, I'm depressed, I have no patience for anything.

I know this is temporary but I feel like I'm losing my mind. Has anyone dealt with this level of sleep deprivation? When does it actually get better?