For as long as I can remember my scrotum has never hung flacid as most mens do. It is almost always puffed up. every now and then It will relax, somtimes after a shower or when I am not feeling well. sometimes its uncomfortable and it feels like my testicle are being shoved into my body. what causes this? Does it have anything to do with me wearing tighty whiteys? Is there anything I can do to eliveiate this condition? thanks

Does it have anything to do with me wearing tighty whiteys?

It's possible that they're not helping. Have you considered changing to a style that gives the boys a little more room (e.g., Briefs w/ a 'pouch'. etc.)?

Your testicles raise and lower in order to regulate temperature. That would explain why they are lower after a shower and when you're not feeling well (i.e., fever).