Go to the hospital. Like forreal that isnt normal.
Best not to have any sex until you are well again and given the all clear from your doctor.
Having sex when there is an unresolved underlying problem could make your condition much worse. If you are sexually active and do not use some form of protection, it may be wise to get checked out for any STD's (sexually transmitted disease).
You do not say if there are any cuts on your penis that the blood may have got on to the sperm, or whether you had a sexual encounter with someone who was menstruating.
If you do have any sores on your penis then that needs proper treatment. If there are no visible problems, it is highly likely that the blood may be in the sperm (like you say) and there may be an infection in the testes or the epididymis or there is an infection in the urethra or your bladder, or a problem with the prostate.
When you go to urinate, observe if there is any blood on the tissue paper and how your urine looks like. If it is cloudy, this can indicate a urine infection.
The doctor needs to identify why the blood is there and where it came from. You may have an infection that that needs treating immediately. Depending on what other symptoms you have, the doctor may prescribe a course of antibiotics. He may order some blood tests to rule out other causes and check your urine sample. The doctor may want to check your prostate gland and may also refer you to a urologist.
Make an appointment to see your doctor urgently.
Let me know how you get on.