Yes need to try to eat food that can help to increase weight. I did try eating durian though, it helps abit. 1.7kg at 33 weeks still okay IF we are talking about you giving birth at full term which is 40weeks. Like mine was birth at 38weeks and birth weight was only 2.6kg. Given an average gain of 150gm per week you will end at 2.7kg at 40 week. So on the safe side, try to eat those food with high proteins.
Oh also, usually the ultrasound weight measurement will differ from actual birth weight since it is just a guide.