What Causes Clear Thick Discharge From Penis While Taking Steroids?

Every time I my prescribed steroids (I think it s prednisone not sure) I get a clear thick substance that will hang from my penis when I urine. This normally occurred after taking for 3 to 4 days. Doctor thought it was std but test were negative. Have not had unprotected sex. Steroids are prescribed for sinus and ear infection and are taken with antibiotics.