Penis skin burning and red few days after masturbation

I’ve been off propecia for 2 years (used it for 7). I’ve had burning, tingling and redness on my penis and testicles on and off for 2 years. ive noticed my penis skin is very thin by the head it usually bothers me after masturbation for a few days then goes away. I been tested for everything including Hiv(blood) syphilis gonorrhea, chlamydia and herpes(HSV1 & 2 blood IGM and IGG) all were negative. Ive seen 3 plus doctors and nobody has been able to help. Has anyone else had similar issues? Any thoughts on how I can get my penis skin back to normal?