Pain or discomfort in left testicle.

I feel a pain or discomfort in the left testicle. Particularly, when I sit for a long time . Sometimes moving around makes me feel relieved from the discomfort. I don't see swelling or any major variations in size. I keep adjusting my pants very often. Particularly when I wear jeans or travel in bus or train, the pain is evident.  I was assuming may be because of my inner garments needs a change in size. I did try it. But still sometimes, I feel a discomfort while sitting for long time. Say 1 hour or more. I did try checking my trsticles with my thumb. I guess I didn't notice anything suspicious. Im so conscious in eating and maintaining good healthy habits. I am about to get married and I'm so nervous to tell this out. Particularly, I have a fear that this might affect my sexual health or make me infertile. Thanks for your suggestions in advance.