What Causes Burning Sensation On The Penis After Unprotected Intercourse?

Hi A day after an unprotected intercourse I had penile tip burning. After a week I saw dr and without test he wrote me doxycycline and other antibiotics after a month I used a more powerful antibiotics. Nothing changed. The only think made the burning so mild is time. It is now 4 month passed. There is a rather white spot about 2mm diameter on my glans after that intercourse without any irritation. Still I have mild irritation and around the opening I feel inflammation and see mild redness. I just mixed the hydrocortisone and clotrimazol creams and rubbed it on my penis for one week, it feels a little better but not completely good. Also all my infection tests and swab came back negative. I dont know what to do, any help?