I used to be a Weight Loss Consultant, when I was in college.
Not for Weight Watchers.
For women, many things can affect varying daily weight.
Water retention.
PMS
Increasing muscle also weighs more than fat. THUS, you may be losing inches, but gaining 'weight' because it is muscle weight. But that is a good thing.
Everyday, all day, the weight of a person fluctuates.
Don't get hung up on every little iota of weight 'gain.'
The ULTIMATE proof, of losing 'weight', or rather, getting thinner... is IF your clothes are getting loser and you are losing inches.
THAT, is the proof.
Not what is on a scale.
Also just a side tip: The body, will get used to an exercise, in about 6-8 weeks. Then the body will plateau. So that means, after 6-8 weeks of a person's usual exercise routine... you NEED to mix it up. Via, the kinds of exercises you do, the intensity, the frequency, etc.
"Interval Training" which is very easy, is a good way to do this. It only can take 10-15 minutes. You basically do any activity, even walking, in spurts of intensity. So, walk at a casual pace for 1 minute, then sprint for 1 minute, then walk slower again for 1 minute, then sprint again for 1 minute. Do it for as long as you can. It is VERY rigorous and will make you sweat. Pro Athletes, utilize this method as well, to get in shape and lose weight.
Do not... get hung-up on the scale. THAT, will sabotage you.
Go by clothes, if they are getting loser, and your muscle tone and fitness.
Right now, you are getting hung-up on what a scale says.
I would never, gauge a woman's weight "loss" by only what a scale says. I go by, her overall fitness and inches lost, in relation to muscle gain.
Accuracy of scales vary. Also it will get affected by what kind of surface the scale is on. ie: hard flooring or a carpet.
all the best,
Susan