Not feeling hunger or thirst for weeks. Doctor says it's nothing.

I've been having many strange symptoms but I'll keep it simple to start. If you need more information in order to give me advice, please let me know.

My Past Diagnoses:
I'm a woman in my early 40s and I'm not pregnant. I've been diagnosed with irritable bowel syndrome (IBS) and iron deficiency. I don't know if these have anything to do with my current symptoms.

My Most Worrisome Current Symptoms:
1) Since January 20th, I haven't felt hunger or thirst, even hours after eating or drinking. I also don't feel the need to urinate until my bladder is almost full.
This is very unusual for me. I usually feel all of these sensations strongly.

2) Since February 8th, I've had almost constant heartburn. And after eating or drinking, I'll have acid reflux that goes all the way up to the back of my throat. Sometimes the acid reflux even happens after drinking plain bottled water on an empty stomach.
I very rarely had heartburn before and I never had acid reflux before.

I don't have nausea and my temperature, digestion, urination, and bowel movements are normal (or, normal for me).

On February 7th I saw a doctor for the lack of feelings of hunger and thirst but he and another doctor he conferred with said it's nothing to worry about. He scheduled a follow-up appointment for Feb 21st and ordered I get blood taken for a comprehensive metabolic panel and a "CBC and auto Diff WBC count" (I don't know what the 2nd one means).

I'm worried that this might actually be something serious and I'd like to be more educated before my next doctor's appointment. I've tried searching online but haven't found anything that matches my symptoms.

Can anyone tell me what this might be? Again, if you need more information, just ask.

Thank you in advance to anyone who'd like to help.