So Confused and Tensed

I have been diagnosed with a hiatal hernia, but I am not sure about its size. My doctor has advised me to avoid core exercises. I am 32 years old, and I love exercising, but I have gained weight, especially around my stomach and lower abdomen, and I don’t know how to manage it. Day by day, I am feeling more depressed because I feel clueless about what to do. Can anyone help me?