I can't offer a guess as to what you have, but I will offer that coughing up blood is nothing to play around with. Seek medical attention promptly. Good Luck!
Good lord, get to the doctor right away. They need to take a listen to your lungs. Sounds like you may have pneumonia and coughing up red blood is a cardinal sign of strep penumonia, this is the strain that can kill you and is the one you get vaccinated against every 5 years. Given your age, if the dr. makes a diagnosis of pneumonia you will be hospitalized for treatment (its standard protocol for anyone over 60), your also going to need to get a chest xray. In the mean time it's a good idea to take a break from smoking pot. Don't play games here, if you really do have s.pneumonia it can kill you.
You may get lucky and just have a case of chronic bronchitis but blood is typically not seen with that.