Is it normal to lose weight while your period?

Before I started my period I have been losing weight. I don't exercise much but the day I got my period i have been feeling heavier, but when i go on the scale my weight is 5lb less than normal. I do eat the right amount of food everyday, but i have no clue why i lose weight now. This is the first time I started losing lot of weight on my period. Someone please help me and my scale is not off or anything. Thank you :)