Pain in lower abdomen and groin sometimes testis. changes sides. swollen veins within scrotum. both sides. what could it be?

Lower abdominal pain: is usually related to a bladder or large intestine problem, such as constipation. It is normal to have prominent veins on the surface of the scrotum when in a relaxed state, but if there is a cluster of veins, it could be a varicocele which occurs in about 15% of men and is usually L sided but usually is painless or dull ache instead of abdominal pain. I recommend you get an evaluation.