Temporary swelling in between thighs

Hi

Can someone try to help me on this. I am a male, age 33.

I get swelling sometimes in between mylegs, to be more clear beginning of my thigh (inside) close to the testicles.

Earlier I used to think it is because of the underwear type I wear...now I am wearing trunk type still I get the swelling...please remember it is not always....in a week atleast once or twice I get this...

Once the swelling appears , it disappers in few hours ...some kind of watery comes out of it and later it will be flat...a normal skin look appears....

excuse my english, I am unable to use the right words...

I want to know what is the reason for this kind of issues...

To reiterate this comes once or twice in a week....and disappears within few hours...I just wash the area with cold water....

anyone has answer..please suggest!