Sounds like a local tissue damage issue to me. Using the cock ring already means you had issues with your erectile capabilities, usually indicative if low androgens. When you have low androgens the chance of injuring your penile (and surrounding) tissues is times higher. It can also lead to symptoms of sexual exhaustion and extreme tissue inflammation even without any apparent injuries.

There is also a slim chance the symptoms could be related to your kidneys. You should see a specialist and not just your primary doctor to rule out any hidden underlying condition (except sexual exhaustion).