I mostly lurk on the site and only hit it a few times a week so I am just finding this thread. Interesting enough I'm going through almost the exact same thing you are. Pain in the right pec muscle when riding, never bad enough to stop the ride, I though it was something to do with my position on the bike. On cold mornings I would get nauseated about 10min into the ride it would last a couple of minutes and then go away (as it turns out this is what really worried the doctor). After about three weeks of testing and being referred to a cardiologist I am heading for the hospital tomorrow for a probable stent. The real lesson learned is listen to your body!