Intense pain at breast bone when trying to eat/drink.

It has been a week now that I have been feeling very unwell. Any food or drink (including water) that goes down my throat hurts/ can be described as a burning sensation sometimes when it passes through the spot located where my ribs begin to fan out and separate (breast bone)

I haven't been able to eat at all this past week. Initially, I speculated it was heart burn because at first it was a consistent pain but it quickly turned into a pain that is guaranteed when trying to swallow something down.

It will flare up sometimes when I'm not eating as well, especially when belching. A week before this all started I had just undergone an endoscopy so shouldn't something have been found then?

I'm really worried because it's very hard for me to gain weight in general and had actually been on meds to gain a couple months earlier and have lost all that progress.

What could be happening in my esophagus?