Every few days for the last two weeks I've noticed small red lines of blood under my skin. They look like scratches but are under smooth skin. Sometimes they are from trauma, like when I carried a heavy bag on my shoulder. Sometimes they just appear, like three that appeared on my chest this morning. I first noticed many of them when I had an automatic blood pressure monitor on my arm when I went to the ER for chest pains (they didn't find anything). I've also been having joint and muscles pains. What might be causing this?