Weight fluctuations occur on a daily basis, depending on what we eat, what we drink, how much we breathe, or sweat, and so on.
If you are finding yourself weighing yourself on a regular basis, and that this is a big part of your life, it may be worth restricting the amount that you weigh yourself. Consider setting yourself a goal, say "I weigh myself each Saturday morning", or something similar.
I would say if you're doing it everyday or more than once a day. Something to help you if you're doing that is start maybe hiding the scale so if you're not seeing it all the time you won't want to weight yourself. Also if you have to weight yourself and you want to weight yourself less often, ween yourself off. So go from everyday to every other day then twice a week and then so on.
I think it becomes a problem when you are beginning to weigh yourself daily or even every second or third day. I think that weighing yourself once a week is fine or maybe twice but when it becomes more than that it might become a problem:)
If you find yourself compulsively weighing yourself, or find that your weight is something that is very frequently on your mind, there may be a problem. Pay attention to how you feel during/after a weigh-in. If the scale has gone up by one or two pounds, do you feel upset? These sort of things are considered problematic when they begin to negatively affect your life or cause you emotional distress.