I have pain in my left testicule and for the last 2 days my semen has blood in it. what could this be? is it an infection? should i take antibiotics?

See a doctor: There is some lab information needed and a thorough physical exam - and a thorough social history exam as well. You need to see a doc for this. Don't delay.

See your doc: Right away. It could be an infection or it could be torsion of the testicle which is dangerous. Peace and good health.

See answer: Symptoms most likely related to prostatitis. If no fever/chills, most likely non-bacterial prostatitis and not a true infection. A urinalysis (and possible culture) can help differentiate. Though an antibiotic may still be appropriate if non-bacterial type, the most useful therapy is: drink plenty of water; avoid caffeine (coffee, tea, pop), alcohol, fruit juices; sitz bath; otc ibuprofen, no sex.