There are numerous factors that could be contributing to this condition. If you have been using a lot of creams, sprays or other medications on your testicles, then it is possible that they may cause the skin surrounding them to thicken. Another possibility is that your scrotum has become irritated due to friction from clothing during exercise or sports participation. This irritation can also contribute to excessive sweating in the scrotum and thus contribute further towards its discomforting symptoms.
Bulky underwear as well as tight pants may also cause increased friction against the scrotal area which can lead to roughness and swelling of these areas. In order for this condition to improve there needs to be a reduction in weariness caused by any causes listed above so it would be beneficial if you take time out from wearing those irritating clothes for at least 10 days before resuming normal activities again (e.g., gym training).