Thanks for your query.Based on the facts that you have posted it appears that you have undergone Vasectomy 6 weeks back and has noticed Blood in the semen ( Hematospermia
Since this has flowed after vasectomy it looks like to be due to infection in the epididymis
or Testicle .
Please consult qualified Urologist
for clinical examination .
You may need to get Ultrasound
scanning of the scrotum and colour Doppler study done to find out the cause of Hematospermia.