I don't know about where you live, here in Chile, supposedly by law the employee has rights, but the actual implementation of the law is very weak. They can always find an excuse to get around the rules and nobody has the resources to take it to the end.
So in part, it would depend on the strength of the law in your area, or the ethics in general in business.
It would help of course if you can document whatyou say, which is hard with POIS... and often, even if the employer could sympathize emotionally, he needs someone to fill a requirement.
You know how it is, he is likely to think, "Well if you want your job, you're just going to have to control your masturbation!"
One option might be to see if there's a way that he could find/create a position for you that is more compatible to POIS. It wasn't POIS related, but one time, I arranged with my employer that I work from home on the basis of performance. It required that week by week, a Gantt chart was processed, that followed the performance of the work that I was performing. Previously a value was given to the advance scale.
This is good for both, although not very common and requires an open minded "boss". But the employer is satisfied becasue he only has to pay by performance, and the employee is satisfied becasue he can adjust his time to suit his condition yet still perform as required.
Even if it's not a situation of working at home, perhaps you could try to see if there is some kind of work to performance plan you could work out with him.
