What else can cause very mild arm pain mild chest pain and nausea besides a heart attack? I've had discomfort all day but don't want to overreact...
Get checked out. The symptoms you describe could certainly be explained by a heart attack. Not everyone has the "classic" symptoms of crushing chest pain when they have a heart attack. There are certainly other possibilities, but since it is unclear the safest thing to do would be to get evaluated by a physician as soon as possible.
Don't contemplate. This can be potentially acute -- call 911 and go to the nearest er.
If I had chest pain +left arm pain on and off for a week is it possible that I had a heart attack without even knowing? If yes how can I check it?
Heart attack. It is low probability in a young woman but not impossible. See your doctor to be checked.