I'd try the ER an hour away. Eventhough your initial ER test were fine, a second opinion is worth the trip.
A couple of years ago I had similar chest pains and thinking that it was just the HUG, I waited for 3 days before the pain got suddenly worse and I went into the ER. The ECG and other tests were fine at the ER.
The next day I went to my PCP and he suspected pericariditis because it got worse when I laid down flat. He sent me for more tests and he was correct. All it needed was a round of antibiotics and to have some fluid drainied off from the sac around the heart. The pain was gone in minutes.

Hope that you get some answers and relief .

With love, Erika