Welcome to Health care magic.
1. The history suggest me that its an inguinal
hernia - on and off swelling in the scrotal sac which disappears after some time.
2. And clothing do effect the swelling which means pressure effect also favours in terms of hernia.
3.Possibilities of
cyst can not be there, because if there is cyst there will be for all time not fluctuation in size.
4.In this case i would recommend to get an
ultrasound scrotum done when you have the swelling.
5.It will exactly help to find out and differentiate actual pathology - weather mass, cyst, hernia - where its existing from and where its extending to - its a good tool for scrotum and testis.
6. You should worry until you find out cause - but nothing is scary in your history.
Hope it helps you. Wish you a good health.
Anything to ask ? do not hesitate. Thank you.