Sorry to hear that you feel like crap, I hope you start feeling better soon.
I'm a serial weigher too, but what I try and do is make one day my "official" weigh in. I check my weight every morning, but I don't really worry if I have a gain from day to day. If I have gained weight on my official weigh in day, then I start looking at my diet/exercise and work out what I could have done better. So if I weigh in one morning and I'm lighter, I use that number to help keep my motivation levels up. If I'm heavier, I just write it off as 'unofficial'