Personal question here, do you have sex often? If not, Do you masturbate often? Males need to have a "release" if you will, once every couple of days. If you haven't had sex or masturbated in a long time, this could be causing the sensitivity.
To answer your question, you really can't give yourself a "self-check" for hernia. Seek a doctor for a physical to determine this.
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The first thing to be ruled out is orchitis or infection or inflammation of testis. Only orchitis will present with some redness and swelling in the testicular area. Pain in testicle could also be due to infection, like prostatitis and epididymitis. Get a culture sensitivity test for both semen and urine done. Also it could be due to referred pain of kidney stones. An ultrasound of the lower abdomen will be able to rule out kidney stones. It could be due to cancer of testis. It could be due to varicocele or spermatocele. An ultrasound of the testicles will diagnose cancer, varicocele and spermatocele. An excruciating pain is often due to testicular torsion and needs surgical intervention ASAP to save the testis. Aside from orchitis and torsion, this can also be due to problems with the protective structures mentioned, testicular dislocation, epididymitis and even hematoma or bleeding. One simple explanation is sexual arousal that does not end in ejaculation can cause congestion in the sperm carrying tubes. This causes a dull aching sensation in the testicle also called ‘blue balls’. Masturbation helps relieve this pain. Hernia and hydrocele are the other possibilities. Please consult an urologist as a confirmed diagnosis cannot be given on net. Treatment will depend on the diagnosis. Take care!