When i wear scrotum support my pain is relifed ? what is the cause? or when i lay down my pain is gone? but when i stand without underwear pain comes back?

We really need a few more details to give a good answer. If symptoms have a come on suddenly over a couple days or hours, then you should seek immediate medical evaluation by physician. If your discomfort is chronic, having been present for months or longer it could be an inguinal hernia. Examination and evaluation by primary care, physician or urologist for diagnosis

You might have a small cyst or irritation in the epididymis. try otc ibuprofen if not better get checked out bu a Urologist