Remembering what you went through a week or so ago, with the TSS possible scare, I think you really need a complete physical. Full bloodwork, urine analysis and if the Dr. Feels like it, maybe an EKG if you continue to have chest pain.
Now, chest pain CAN be heartburn, from stomach acids goin back up the esophogus, and it has frequently been confused with a heart attack, but it usually isn't unbearable pain, even though it's strong pain.
If what's going on is something like a panic attack, well I don't know what to do about that. As for forgetting to breathe, try singing outloud. Loudly, so that you must breath. Try Opera like loud.