Tracking is so important. If you didn't become obese because of a disease (like a dysfunctional thyroid gland) or long bedstay after an accident, then your problem is in your head--mental & emotional.
In other words, what you're up against is probably less physical than it is mental.
An easy way to determine this is to keep a food journal. Write down everything you put in your mouth, whether it's just sampling from a ladle to see if the soup needs salt or eating that spear of asparagus someone left on the plate as you're scraping off the food before dishwashing. EVERYTHING.
My experience all my life in a huge family with constant extended family gatherings and church potlucks is listening to people with their mouths full of food, chewing and at the same time saying, "Oh, I've got to reduce." That was back in the day before people used the word "diet."
If my relatives were confused and frustrated about their weight, they never did the one thing they had the power to control: track every bite.
Assuming you don't have a physical condition that's causing your nausea & other symptoms, get a journal and start tracking. And don't lie to yourself or say, "Oh, that's doesn't count. It's just a piece of lettuce." YOU'RE FAT! OBESE! OVERWEIGHT! You have an eating disorder, even if it's not bulimia or anorexia. If you didn't have an eating disorder you'd be of normal height and weight. You probably look forward to eating more than any other activity in your day.
I wrote this post as if I were talking to myself because these were the thoughts and actions that used to rule my life. This is why I became obese and RYGB was my final alternative.
After surgery I lost 115 pounds in 14 months. I've kept most of it off since I hit my goal in 2009. But I've also experienced some slacker time when I ate lazily and gained 20 pounds because unfortunately, you can't have brain surgery to change your psychology. But for sure, I never want to be morbidly obese again and I'm getting old. I remember reading that by the time you hit middle age, you have lost about 35 percent of your ability to burn calories.
Just get a journal and keep it with you constantly, Write everything down, from what you eat to what you think. Talk to a therapist. Talk to your surgeon. Talk to us. We support you.