I think your priest is in a better position to advise you on this than any of us. Trust what he has told you. None of us are pastors nor are we certified clinicians or diagnosticians.
Obviously, I can’t speak to you personally, but – generally speaking – I can certainly see where some people’s personality disorders would reduce their culpability greatly and severely impede their ability to freely consent to sin (which is, of course, one of the three prerequisites for a sin to be mortal).
Certainly, as the other Joseph said, we want to resist sin to the best of our ability. You wouldn’t want to take the priest’s counsel as a “license to sin” without a care as to the consequences. But, from your previous posts, I doubt you are in danger of doing that.