Unexpected weight loss or gain.
I would agree with the others advice, see a doctor quickly. Cancer is may not be the cause. A few years ago I experienced massive weight gain for no reason. I upped my workouts and the weight kept piling on. I had some blood work done and found my thyroid stopped working and caused a chain reaction in my body that slowed my metabolism and caused my weight gain. The doctor told me I had hypothyroidism and continued to say there are two types hypo and hyperthyroidism. It sounds like to me you have hyperthyroidism, which will call massive weight loss no matter how much you eat you will continue to lose weight. If not taken care of, it can result in serious issues with your liver, kidneys and other vital organs and will result in death. If you have hyperthyroidism, they will remove your thyroid, only a minor surgery and place you on thyroid meds to balance your body levels out. My thyroid shut down, which means I also have to take meds every day to keep my levels normal. Good luck.