What Is The Treatment For Swollen Foreskin And Discharge?

I am a sexually active male, middle aged, in a monogamous relationship. I was unfaithful quite some time ago during a brief break up period, but only now, months later has this happened to me. Initially, I had a burning sensation during urination, thought it would stop, then flu-like symptoms. But now my foreskin is really swollen and there is semen like discharge. Quite painful. What could this be?