Paxil and SSRI's are known for having sexual side effects....
But opiates are even more well known for this. I am an ex-opiate addict(oxy and H for 5 years), and took Suboxone(partial agonist opiate) for 2 years, and throughout that period of time I had some serious erectile/sexual problems. There were times, when I was last dating, that I would last for over an hour, and then just give up and go limp. :P
I would say it's probably the Dilalauid, but the Paxil could possibly add to it as well. I would recommend some herbal supplements like Maca or other herbs that generate sexual function. Then there's always Viagra.