baby only gets sick at night

My daughter (12 days old) is great during the day-- eats well, naps well, etc. But at night, she has terrible tummy issues. Gassy, throwing up (not just spitting up), fussy all night and into the morning. Gas drops haven't helped. We're not seeing huge changes with sensitive formula, although I am giving it a bit longer. If it's the formula though, why isn't it making her sick during the day? She already sleeps at an incline for both her daytime naps and at bedtime.
And before anyone rails on me about breastfeeding, I have severe supply issues due to hormonal problems. I'm lucky to get 2 ounces with a whole day of pumping. I am, however, saving all the milk I am pumping for the moment to see if it's something in my diet that's making my daughter sick.
We have her two week checkup in a couple days, so of course I'm going to talk to the doctor about this. But I was wondering if anyone else had a similar experience, and what helped. My older daughter had zero stomach issues, so I'm at a complete loss.