Eh, at 16 weeks mungkin tu adalah baby movements mixed dengan Braxton Hicks (perut mengeras), both boleh happen sebab rahim tengah membesar, especially waktu malam bila you're lying down and more aware of it. Since this is your first pregnancy, the sensations memang confusing, a few of my mum friends thought they were having contractions tapi actually just the uterus stretching and baby moving around, terutama kalau terjadi bila you shift positions. Siang kurang terasa sebab you're busy with daily activities je. Tapi sebab you have low BP and low HB, better check with your doctor next visit to make sure semuanya okay and get their reassurance, dapat peace of mind lebih bagus dari guess-guessing, kan?