can dogs get constipated? How do I get him to go?

He has a bump behind scrotum and he yelps in pain if I try to pick him up?

Go See Your Vet Surgeon,He will tell you what is best,Also get him checked out he may have some type of tumor

that doesnt sound like constipation, that sounds like prostate problems, or anal gland impactionyou definatly want to see the vet, but in the mean time, if it is either constipation or anal gland impaction, either pumpkin or papaya will help ease both make your appointment sooner rather than later though, because sometime anal glands rupture and that can be fatal