Bloody semen should i be worried????

i work as a custodian, and during the summer time we clean rooms, and ive been lifting heavy furniture, and i feel like i strained something in my abdomen, and about two months ago i noticed blood in my semen, than it went away for a while than the other day it came back, i dont know if it was from lifting something or if there is something wrong....some websites say its nothing and some say theres something wrong, im confused...*also im 20 yrs old and not ualy active*