How many weeks pregnant are you? 20kg or about 45 lbs is way too much weight gain for pregnancy. You should gain only about 20-25 lbs (8-10 kg) throughout the whole pregnancy. There could be several reasons as to why you gained excessive weight: you might have an underlying condition creating excessive water retention, which will make you weight creep up significantly, your face, hands and feet could be puffy and swollen. This needs to be discussed withwith doctor to make sure nothing abnormal is going on.
The second reason is poor dietary intake. Make sure you are NOTNOT eat anything sugary or starchy at all, that includes fruit juices, bread, pasta, potatoes, processed foods, bar snacks, cereals, candy, soda, bananas, grapes. Focus on consuming good quality fatty meats, green vegetables, eggs, cheese, fish, full-day dairy, some berries for dessert. These foods will keep you satisfied and prevent you from snacking on junk. You need to avoid every food that makes your blood sugar spikes. Look into low carb diet.
Did you get tested for diabetes? Even if you passed the test, you might still want to check your sugar one hour after each meal for few weeks. Ask your OB doctor to prescribe a glucometer and testing supplies to you. See for yourself what foods cause sugar spikes and avoid those at all cost.
Your weight gain is concerning, because it can cause a large baby, difficulties in labor and diabetes later in life for both of you. Do not listen to anyone who tells you it's okay to gain so much weight. Please talk to your doctor as soon as you can.