Hello there and thank you for your question!
There are many other factors that can influence your weight other than your diet and physical activity, such as your age, gender, metabolism, environment and even certain medications.1 It can be difficult to point out what exactly may be causing your weight gain since it can be caused by multiple factors. I suggest you to consult with your doctor or other qualified health professional and assess your overall health to help explain what may be going on.
If you are still suffering from an eating disorder and wish to recover, I encourage you to reach out for support from someone you trust. This could be a family member, a close friend, a counselor, a therapist or doctor. Be specific about how this person can best support you (e.g. help you find treatment or accompany you while you call a helpline or see a doctor or therapist).
Helplines for eating disorders
U.S.: National Eating Disorders Association, 1-800-931-2237
UK: Beat Eating Disorders, 0345 643 1414
Australia: Butterfly Foundation for Eating Disorders, 1800 33 4673
Canada: National Eating Disorder Information Centre, 1-866-633-4220
Hope this helps and wishing you long-term health and wellness!
1. Institute of Medicine (US) Subcommittee on Military Weight Management. Weight Management: State of the Science and Opportunities for Military Programs. Washington (DC): National Academies Press (US); 2004. 3, Factors That Influence Body Weight. Available from: https://www.ncbi.nlm.nih.gov/books/NBK221834/