Weight gain in twin pregnancy in the seventh month of pregnancy should be one and half pounds per week. Your wife has definitely gained less in the last month but if she now eats a healthy nutritious diet prescribed by her gynaecologist, this deficit can be made up. An ultrasound can be done to assess foetal well-being. For pain, which could be preterm pains, instead of Duvadilon we have better drugs like Depin to control pre-term pains, which should be prescribed under the care of an obstetrician.