The area around my testicle (i think the epiditimys) is inflamed and sensitive what is the most likely cause?

Depends. If your epididymis is swollen it could be from trauma recently such as extended bicycling etc. As well as possibly a mild infection known as epididymitis. Sometimes this can be associated with prostatitis as well. In the latter cases, antibiotics would be appropriate, but in all cases rest, anti inflammatories like Ibuprofen and supportive wear are helpful -check with your doctor though.
? Epididymitis. Or epididymo-orchitis. Could be from a urinary or viral infection, std or prostatitis. Worth getting a urinalysis plus urine culture if positive. Antibiotics, rest and ice pack should speed up recovery. Best to see a dr., necessary to get a prescription.