I had blood in my sperm last night when i ejaculated during sex. it burned a bit and now it burns when i use the bathroom. what can it be? i am 28 yo.

Possible reasons:: Blood in the sperm is called hematospermia. Sometimes it is due to infection. In older guys it could be a sign of cancer. But often, nobody knows why it happens. Get checked this week but don't panic! See this wonderful article: http://www.harvardprostateknowledge.org/hematospermia-demystified

See doctor: Bloody semen and painful urination can be caused by a number of things. At you age, one of the most common is an infectious disease. A visit with your doctor could determine the cause and provide treatment to eliminate your symptoms.

Blood in sperm: I would certainly recommend a visit to a urologist ASAP as this is not a normal occurance.