What Causes Swelling In Testicle?

My right testicle is slightly higher than left, and feels very slightly larger. Ive been experiencing a tugging sensation when i do normal things like walking, standing up, etc. Their isn't really any pain, its more of a discomfort. Also, anytime i have an erection it worsens exponentially and i can feel hard lumps on the bottom of my testicles. What's wrong with me?