Anyone work shifts?

I went back to work last week, and M-W I was working days, and pumping was going well, I was pumping 18-24oz at work, and LO takes 28-32oz/day so I was more than keeping up. Then I had to work thursday night, and then 24hrs Saturday morning to sunday morning.  My supply seemed to drop over this time, to the point where Sunday I only was able to pump about 10oz and then nurse in the afternoon and evening, and I ended up giving her a bottle of EBM at bedtime because I just didn't have enough milk for her to nurse.  This morning before work I pumped and only got about 5oz, compared to the 7-8 I usually get in the morning before work.  My question is, does anyone else who works shifts find that it really messes with you milk supply? or should I be investigating to find another cause. 

TIA!