Hello, could you please tell me how I can get back in shape after givi…

Hello, could you please tell me how I can get back in shape after giving birth, it's been nine months, I am breastfeeding, I have no appetite, I eat more than the norm - it starts to feel sick, and the norm is two times a day and that barely, mostly I will drink tea and don't want to eat, my height is 168, weight is 52-54 kg, one word skin covered with bones, already even my husband said that if I don't get back in shape then we will break up. He's joking (but still...) Maybe there are some pills or vitamins that help gain weight and stimulate appetite? Thanks in advance for your answer.