Progressively worsening ED post RALP

I had my RALP about three and a half months ago and things have slowly deteriorated on the ED front. I thought I had had an incredibly lucky recovery with nocturnal erections with the catheter still in days after surgery (a bit painful but I wasn’t complaining!). Then very successful activities after 4 weeks (with 100mg of viagra admittedly)! Almost back to pre surgery levels. I thought it an utter miracle and couldn’t believe my lucky stars. After 8 weeks though I noticed things weren’t quite as good - I could achieve the deed but not easily. Finally after 3 months things have deteriorated even more and I now really struggle to get a half way decent erection even with pills.
I read what Dr Mulhall writes about this and he says the 3 - 4 months is the worst time for ED post surgery. Certainly what I am finding and sadly my miracle recovery may not have been all that rosy after all - it did seem too good to be true at the time. I was wondering if others have gone through similar? Pre surgery I had thought the getting worse over time was more a brachytherapy effect whereas surgery was more about improving over time. Obviously not in my case anyway. I hope the good doctor is right that 3 - 4 months is the nadir and that after that I should start to see a gradual improvement?

With ED, to some extent you are fighting age as well. There was a study in North Carolina where over 20% of patients on Active Surveillance reported some ED at the 2-year mark. Since nothing was done to them, one can assume that it was age-related.