Although I am not a doctor, this looks a lot like ascites, which is fluid retention within the abdomen. It's commonly caused by excessive drinking of alcohol over many years and can show up quickly once the body's lost a lot of its ability to filter fluids (I don't know the technical terms around that-- but mine developed over maybe 2 years after 10 years of heavy drinking). It can also be cause by other things like congestive heart failure or clogging of vein within the liver.

As I mentioned, I had drank heavily for years (2-3 20oz sugary colas in the afternoons and alcohol in the evening) and was developing a similar condition. I quit alcohol and sugary beverages entirely and dropped about 45 pounds with no other interventions (essentially, I lost all the weight in my midsection) over the course of maybe a year and a half. So the weight loss was slow but steady.

Your case definitely looks like fluid retention to me, but since I don't know you, I am not sure if that ends up being true and if so what factors are contributing towards it. Diets heavy in salt can cause fluid retention too. So if you're eating frozen microwavable meals, many types of fast foods, or cans of soups (or really any meal that has high sodium), that can be something you target to eliminate from your diet.

I'd recommend getting a second opinion from a doctor that looks into liver functioning and heart functioning, but specifically mentioning exploring whether ascites might be a possible diagnosis. There may be some underlying condition that's causing the fluid retention that hasn't been identified yet. Best of luck! ✌