I just want you to know my opinion on this matter. It is not to scare you by any means but it could also be what is going on with you...I had the same thing happen to me and I went to the ER because of the coughing up of blood. It also hurt when I would take a deep breath. they did a chest x-ray and all looked good and they thought it was just a viral thing but did another test just to be sure and I ended up having 3 blood clots in my lungs. the test they did is called a d-dimer test and normal levels are 1-400 and mine was 2120 so I was super sick. They did a cat scan to see where the clots were and they were in my lungs as I stated before and was admitted to intensive care for 1 week and was given blood thinning meds untill my numbers came down and now I will take coumadin for the rest of my life. Please be very persistant and not just give in to what the doc said. my family doc said he would have just sent me home with meds and never thought of a blood clot and he was very impressed that the hospital ran that life saving test for me.