hello

this is my first post I have just been reading threw old post for the past week. so I have a problem I have been lifting weights for the past two months and have noticed that one of my testicles disappears while lifting heavy weight. I have asked my doctor and he said since there is no pain with it that it is not a problem. has anyone else had this problem? it worries me so I was wondering if it is common. I am a healthy 24 year old and have no other problems.any help would be great thanks.