What Causes White Round Blisters On The Penis?

I am a 52 year old man. I have noticed in last 6 months : 1. Inguinal gland swelling , it was tested and found non malignant 2. My penis developed white round blisters and it became itchy and retraction of foreskin was difficult 3. I consulted a dermatologist who said it is erosive LP and gave a strong topical steroid 4. After 3 months he gave another topical steroid 5. It is now 6 months but if I do not apply topical steroid then penis glans become red , white skin peels and it becomes red and irritable 6. Do I have to continue this topical steroid forever 7. I had multiple sex partners in last three years 8. Now my oenis size is smaller , it has developed an upward curve and sexual desire is less 9. I want to get a full sex test screening done to rule out any STD , what test and where to get it done ? 10. Any connection between swollen Inguinal glands and my penis condition