Chest pains over several days

I have had chest pains for about 4 days. It felt like as if I carried something heavy and it was muscle pain in the center of my ribs. On Saturday night I decided (I write this Monday), I went to ER. After about 6 hours waiting, I had blood test and ECG test and both were fine. All levels were normal. I was on a drug called Doxycycline for 5 days to get rid of a urinary infection when I noticed this was occuring shortly after I started taking them.

I mentioned to the doctor/nurses about this and I guess he came to think it was a reflux issue. Only thing I've done is take Maloxx for anti-gas/anti-acid reflux. but its not changing anything.

I also informed the doctor that I notived a flat bump that was sore to touch at the bottom of my sternum. He said it was just part of it. Could this be something else?

I'm someone who panics with stuff like this so I think I had a bad anxiety attack and couldn't sleep last night. Finally got to bed around 8 this morning.
At this moment the chest pain is not as hard as it was 2 days ago, and I just have the odd little discomfort, and the flat bump at the bottom of my sternum.(which is hard but still hurts when I rub it)

I have a follow up with my doctor on Thursday, but I figured I'd see what others have to say on here.

Thanks for your time.