NSFW: I'm extremely worried about a health issue, and I'm not sure whether to contact a doctor. Help?

4 or 5 years ago, I was diagnosed with testicular torsion, and had surgery for it three years ago. And last week, I had a physical exam and everything was ok. But today, I noticed that when my bladder is full, and I really have to use the bathroom, my testicles shrink and get firm. Is this normal? Does this happen to any other guys?