How often do you need to weigh yourself when you are trying to lose weight?
It is really a personal choice, but I do recommend NOT weighing in more than 1 time a week. It can be discouraging to see that number either change very little or not at all or even go up sometimes.
Your weight fluctuates throughout the day with temperature, water retention, and food intake.
I think that weighing yourself once every 2 weeks or so, is plenty enough.