Losing weight instead of gaining

Hi mommies.. since the first day tau pregnant sampai sekarang (15 weeks) saya timbang badan and nampak saya makin lose weight dah 1kg lebih dah. Agak risau sebab bukan ke kena gain sikit? Baju and seluar dah start tak muat so macam tak tau kenapa losing weight. Ada ke mommies macam ni? Okay ke?