Is cancer anxiety a real thing? i feel like im losing weight when im not is this a sign of severe health anxiety?

Sounds like you have a true emotional issue that could be handled, controlled, and potentially reversed. Be proactive and deal with this ASAP. Have seen success with cognitive-behavioral therapy, biofeedback, acupuncture, meditation, and regular aerobic exercise. Pills work temporarily but are not the ultimate solution.

It is not feasible to provide an opinion without additional history, physical examination may be some tests. It would be prudent to see your doctor to see if you may be depressed. Depression is treatable. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!