I had reflux occasionally in the past, now I am having all sorts of upper GI problems, chest pain, upper back pain, acid, etc. I was sure I had an ulcer but I had a negative endoscopy. I suffered from extreme anxiety over my stomach for months, which I'm pretty sure didn't help the situation any.
I think I have probably developed full fledged GERD but I am trying to stay off medication for it. Maybe your costochondritis is actually GERD? I wonder because I myself have central chest pain right around my breastbone, which feels almost mechanical, not organic, but I suspect is gastric. I have to have an abdominal CT scan soon, don't know what they'll find.
I have read in various posts on this board that whatever conditions a woman may have before Peri, worsens when Peri hits. So maybe that's the answer, it just got worse...