Sir...my Child 3.5 Years Old Wont Sleep Properly During Night

sir...my child 3.5 years old wont sleep properly during night times and he is not interested to have food also properly...his height n weight both are less compared to his age...shall i give cypon syrup fr him daily once during night times fr his proper growth....this vl cause any problem fr my son?else suggest me any proper solution fr my son growth please