Bonnie, welcome! I think something that may be helpful for you is to consider what led to weight gain back in elementary school to begin with. Is it something emotional possibly? When there is a high level of emotional stress or emotional avoidance of something (which can persist from childhood throughout adulthood), that can most definitely lead to weight gain and metabolic issues, so you may find some answers there. Especially if eating adequate calories and good food has not helped.
Another possibility is that you have something hormonal going on, like PCOS or elevated estrogen or something. Regular exercise can be extremely helpful for these conditions, so you may have better luck there. GoKaleo.com is a good blog that a lot of people here follow. She was obese and had great success losing weight by combining exercise with adequate calories.
Best of luck, and my best advice is anything you can do to truly love and take care of yourself will be helpful for life, even if not weight change.