Do I have pneumonia, bronchitis, or another lung problem?

I've had a bad cough for the last 4 days, and i don't feel bad enough to stay home from school, but this morning i coughed up a tiny bit of blood for about a half hour. I'm tired all day, but don't feel short of breath. When I get to the top of my breath, it gets itchy in my lungs and i have to cough, and usually produce mucous. I also had headache all day. What do I have? Thanks!