I have severe anxiety and for the past few days, I have completely loss my appetite, no desire to eat period. Is this my anxiety causing it?

Adrenaline. When you are anxious your adrenal glands will secrete extra amounts of adrenaline which is part of your sympathetic nervous system (sns), sns stimulation decreases appetite, decreases salivation, decreases overall GI function. So the answer is yes. If this problem is continuous or severe see your doctor.
There is help. You should see your doctor and have an evaluation. To make sure there is no medical condition such as thyroid disorder or other hormonal imbalance. Also a psychologist can help with cognitive behavior therapy.
Yes. Anxiety can definitely cause loss in appetite. If your anxiety is so bad that it's affecting your ability to function, you might consider getting a consultation from your physician or a mental health professional. Hope this answer helps.