I believe I need way less calories than most people and that's why I gain weight so fast. I would like to know if there is a way (like with professionals) to actually test how many calories I do burn in a very ordinary day?

I eat about 1800 cal per day and I stay at 260. I did yoyo all of my life and I've had the sleeve bariatric surgery in 2016, I did lost 90 pounds but then I got to alcohol big time. I am now almost 20 months sober. It did made me lose about 50 pounds just like that in about 3 months, but I don't lose no more. My habits are very normal, I do not suffer from an eating disorder (thanks therapy). I don't move enough I guess, which makes me think that 1800 cal per day for a sedantary lifestyle shouldn't make stay at 260 lol so I just burn less than most people?

If there's a way, I could find the required professionnals to help me figure out what maximum cal to do CICO. Btw the 90 pounds was lost over 9 months but I did eat like a baby for the first 2 years or so, now I guess I eat like a 10 years old (portions I mean lol...)

Thanks for any help :)