Hello and welcome to HCM.
I understand your frustration. Let me first explain to you, that this is not normal, and I am sure you are aware of this as well.
At first, please visit a doctor for a physical examination. An abdominal examination could greatly help in palpating any lumps, masses, etc.
Next we could conduct an ultrasound
of your abdomen and pelvis. If your appetite is normal, and according to you, you have no fear of gaining weight, then two of the main conditions have been ruled out.
Please do not worry, as there could be another cause to this. An ultrasound scan and even a CT of your abdomen and pelvis could detect any possible cause, that could be causing a drastic drop in your appetite. Once this cause is identified, your doctor will be able to put forward options of treating/excising this. Once this is done, you should be able to live a stress-free healthy life.
Wishing you the best.