Let's define true weight.
I don't think you can weigh at the same time under the same circumstances at different intervals and come up with a true weight. There are factors a person can not control, such as eating the same amount of food the night before or drinking the same amount of water, stuff like that.
I weigh myself every day. I know what and how much I eat the night before and I know how much water I drink the night before and I see the differences on the scale the next morning.
What I would recommend is weighing yourself every day, Monday through Sunday and then take that average.
The next week, do the same thing, weigh yourself every day, Monday through Sunday, then take that average.
Subtract each "average" weight and I think you will come closer to a more accurate representation of your
weight loss.
Let's do some numbers:
Monday - 150
Tuesday - 150
Wednesday - 149
Thursday - 149
Friday - 149
Saturday - 148
Sunday - 148
Average Weight = 149
Monday - 147
Tuesday - 147
Wednesday - 148 (bad food day)
Thursday - 146 (extra exercise day)
Friday - 146
Saturday - 146
Sunday - 145
Average weight = 146.4
Starting weight 150 minus ending weight over two weeks 145 = 5 pounds.
Average weight first week 149 minus average second week weight 146.4 = 2.6 pounds.
Now the question is: How much
body fat have I lost? 5 pounds vs. 2.6 pounds. Can we say that half of the weight loss was water and the other half body fat?
We all know that initial weight loss tends to be water weight. If it's really hot and I've sweated a ton but haven't replaced all of my fluids lost, then I will lose water weight. But surely we can lose some body fat with that water weight.
Most people on this forum do not advocate weighing every day. "Look in the mirror." I agree with looking in the mirror. I do it every day. But I also weigh every day. That way I can catch any major weight gains before they get out of control.
Personally, I can gain 10 pounds of water in one or two days and lose it just as quickly. But when I see that 10 pounds on the scales, it lets me know it's time to get it off.
Every one is different. But I wouldn't sweat "that time of the month." If it really bothers you, then weigh every day but keep a log of "that time of the month" and see how your weight fluctuated during that time.