This app was mentioned in 2 comments, with an average of 2.00 upvotes
This sounds like regular fluctuation. The best way that I've found to track weight is to be consistent with it and take an average. Weigh yourself in the morning after using the bathroom and without any clothes, and do this daily. Each week you can take an average to determine what your actual loss or gain is. Your weight will fluctuate daily and this is normal. If you have a smartphone, there are apps where you can just plug in your weight and it will calculate averages for you. On Android you could try WeightFit which is a good no nonsense app. I can't speak for iPhone apps.
Whoa. I wonder how accurate that is.
Here's the app I used