Coughing Up Bloody Sputum, with a History of Pneumonia

About five months ago I coughed up copious amounts of blood. Before this, I was feeling fine with only a very mild cough (a couple of coughs a day). For whatever reason, I coughed one very hard and very loud cough, and then immediately after began to cough up a lot of blood. The more I coughed the more came out, and I felt like I had to keep coughing. After a couple of minutes of just coughing out blood, I decided to forcefully suppress the cough and, though I felt like I really had to cough, managed to not do it for the rest of the night. The next morning, continuing to suppress all desire to cough, I went to my physician and got chest x-rays which indicated I had pneumonia. I thought the diagnosis was strange because the coughing had just started the night before and I had no other symptoms. The doctor prescribed me extra strength amoxicillin and sent me home with instructions to go to the ER if I coughed up blood again.

Sure enough, the next night I couldn't suppress my cough any more and once more coughed up a lot of blood, until the point where I finally managed to stop. I went to the ER, got more x-rays and blood work. The blood work came back fine, but the chest x-ray just continued to indicate I had pneumonia. By this point, I had continued coughing to the point where my cough became unproductive and no blood was coming out when I coughed.

I went home, and did not cough up much the day, except for (relatively) small quarter-sized clumps of blood every now and then. The next night, I had a strong urge to cough and couldn't control it. Fortunately, I was not coughing up blood but to my surprise I coughed up a small (centimeter sized) cylindrical plastic part that I vaguely remember being part of a toy I used to play with about 7 years ago that I guess I must have accidentally inhaled. Next day I went to my normal physician who suggested I go to a respiratory specialist who speculated that the foreign body had made me susceptible to pneumonia and that because I had expelled it, I should have cured myself. (He also up-ed my antibiotic to a different kind). After this point, my coughing got less frequent and so did the blood. Three or four weeks after the initial episode, my chest x-ray showed that I no longer had pneumonia.

However, about a month ago, I started to expel a lot of mostly white and yellow sputum with rare specs of blood. At times the sputum is even rust colored. Again I do not have a fever or any other symptoms that would normally indicate pneumonia or other respiratory illness/infection, and I am not coughing at all, just spitting out the sputum. I am unsure however if this phlegm is coming from my sinuses (I don't feel any pressure there) or my chest (which feels perfectly clear and I can take deep breaths). The blood is also not a lot at all, especially when compared to the amounts I originally coughed out, and came weeks after I started expelling the white and yellow sputum.

My theory is that for whatever reason my sinuses are acting up and producing a lot of mucus, and that through expelling it for weeks, I irritated something along the way which has resulted in some blood in what I expel. However, I do not know much about this, and would love someone else's help. In fact, I am not fully convinced that what caused the bloody cough five months ago was a bacterial infection. I think that because I coughed so hard right before, that I may have popped a blood vessel somewhere in my throat, bronchi or lungs. This then would have caused blood to flow into my lungs, giving the appearance of pneumonia on the chest x-ray. But... I have no way to prove that.

Sorry that this whole thing was so long, but I wanted to include what I thought was important past history. (Also, I am a non smoker, 20 years old, and in decent physical fitness, with no other health issues.)

Thank you for your help!