Dermatitis on the head of the penis (I tthink balanitis is being described) could be caused by to certain soaps, or contact that precipitates allergy. This could even be from spermicide from a condom.
I think this is what he described. The first time it appeared was after I had intercourse using a condom, which I had not used for a long time prior to this occasion since I was in a long-term relationship before.
Since then (July) I have had three other sexual partners and it seems this problem occurs after using condom each time since the head of the penis then is quite sore and irritated, which lowers erectile functioning.
I am curious that it may be an allergy to the spermacide or to a particular soap?
Another possibility is infection.
I had STD test with that GP and he cleared me from that possibility.
I would just check if any new products were used in association with the start of your symptoms. I would also see the GP again in the first instance to ensure any infection has been ruled out - with appropriate antibacterial or antifungal prescribed if this is a potential problem. If this doesn't yield a result in terms of diagnosis or treatment then it is well worth seeing a urologist for another opinion on viewing the area.
If you are uncircumcised a relatively common problem is the build up of smegma just under the foreskin that can cause irritation and lead to dermatitis on the head of the penis. If you gently retract your foreskin and wash the area you may find some smegma that can be washed away. Sometimes this is difficult for men with a tight foreskin.
I go to the gym so I probably shower and clean that area thoroughly 2 x times per day.
I hope this information is useful, feel free to reply for any clarification
Any further pointers would be appreciated.