Hello and thanks for posting,

An overactive muscle causes a testicle to become a retractile testicle. The cremaster muscle is a thin pouch-like muscle in which a testicle rests. When the cremaster muscle contracts, it pulls the testicle up toward the body. The cremaster reflex can be stimulated by rubbing a nerve on the inner thigh and by emotion, such as fear and laughter. The cremaster is also activated by a cold environment. If the cremaster reflex is strong enough, it can result in a retractile testicle, pulling the testicle out of the scrotum and up into the groin.

You may just have this tendency. Try and relax if you can, and consider taking a warm compress/wheat bag into the consultation with you, and apply it before a doctor needs to examine you. The same goes if you need to have an ultrasound. They won't mind, if you ask to do this, and will give you privacy beforehand behind a curtain. 

I hope that things resolve for you soon, 

Best wishes,

Vanda