Starting a new journey

Hi, I am Pam and I am starting my new journey. I will be 50 yrs old this September, I am 5'7" tall and when I started my journey on Monday I weighed in at my heaviest at 350.8 lbs. I have severe degenerative arthritis in my knees and lower back and fibromyalgia. Some days are tough to even get out of bed, but I am making myself fight through the pain. I go to the wellness center pool as much as possible because in the water my body will let me exercise without the severe pain. I normally swim from 1 to 2 hours at a light/moderate pace. I am preparing to have a gastric sleeve so that I can lose the more than 120 lbs that is required for me to be able to have my knees replaced. I have been big my whole life and 300+ lbs since 1994, so dieting and exercise alone does not work for me as I will yoyo. Hopefully once I have my surgery I will be able to drop the weight permanently and keep it off. I have to lose 200 lbs in total so it is going to be a long hard journey even if I get to have my surgery.
I have been to the pool 4 days straight, taking the day off today as my body says I have to, and I have lost 3 lbs already so I am very happy.