Wa'alaikumassalam sis! Honestly, at 17 weeks with dizziness and nausea like that, better check with your doctor first, some pregnancies just tak boleh puasa, especially if you're already having these symptoms. A few of us mums in the group, some managed to fast in second trimester tapi ada jugak yang kena skip it sebab similar issues like you, and their doctors advised against it for their safety and baby's. Your health and baby come first, so get the green light from your gynae before you decide okay?