These are my opinions, not proven facts:
1) After avoiding pornography and other arousing explicit content for a while, your PE will lessen. It is our haste to reach a high that conditioned us to finish sooner rather than later. Hence, as you stay clean for long periods of time, the PE will improve, it did for me.
2) Step one above will get you to a better place in regards to PE, but from that point, to improve more, talking with your wife and asking for her help with the process of learning to desensitize, can be helpful. This can be a sensitive topic, and from my experience, try not to get offended or defensive when talking about this,and if need be, just listen to your wife's concerns. After you both talk openly, she might be able and willing to help you work on desensitizing. Depending on your relationship, you might need to work on your open communication first.
3) If you feel comfortable, talking to your Rav could be helpful, he might have other ideas and advice.
Good luck.