You're not going to like this but I think his problem is that he wants to have sex, just not with you. But that's fixable. Right now he's got a problem with the expectations that he's developed from porn, movies, and other media in that he expects a woman to be a particular type of seductress all the time, craving sex, moving sexually, wearing sexy clothes, talking dirty, etc. and you're not fitting that fantasy. So, he uses porn to get him going and the women he looks at to play that role. Once he's jump-started things and is horny, he doesn't need that, he needs a hole to have sex with, and that's a role you can still fill.

I don't think he's trying to be disrespectful, but he's just not finding you sexy, and that's not your fault. The issue is entirely about managing expectations. You don't feel sexy all of the time, no one does, but the women in the videos are sexy all the time, because he sees a tiny glimpse of them in which they are sexy, so to him that's 100% of their life and personality, it's just not realistic. His comment about you not knowing how to be sexy was his poor way of reaching out and asking you to try and meet him in the middle. He wants some of that fantasy. Wear lingerie, talk dirty from time to time, initiate some spontaneous sex, blow him when he walks in the door one day, give him mischievous winks when out in public and graze his groin with your hand. It's all role playing. Just play the role of the insatiable woman who craves him from time to time. Become his porn so he doesn't need porn.

At the same time, if you're willing to make that effort, he needs to understand that no woman acts like a porn star all of the time, it's just not reasonable. A big part of sex is about making the other person feel desired. He needs to play that role too. He needs to make you want to do those things for him, and looking at porn before sex does the opposite. This is where communication comes in. You need to let him know how you feel about what he's doing and he needs to communicate his needs and wants in bed. Discuss both of your expectations and see if you can come to a middle ground. If he can't or won't curb his need for porn, and you can't or won't find ways to spice things up then perhaps you're incompatible in that department.

One last thing, and don't take this as me putting this all on you, but every time you mentioned having sex you mentioned that you had gone to take a shower. I don't know if that was coincidental but if I knew I was going to have sex and then I had to wait for my SO to go take a shower, I'd probably start looking at porn while I waited too. It's just not sexy to have someone let me know that this were going to happen, thereby starting my engine, only for that person to leave the room for a while, leaving my engine idling, and expect me not to get things going myself in the meantime until they came back. If you're the type of person that has to shower every time you're going to have sex, then maybe things are feeling a little too clinical and procedural for him rather than the lust-fueled passionate sex he knows is possible, even outside porn. You also mention him initiating every time, so perhaps he doesn't feel wanted in that regard. You might consider seeing a sex therapist to help you relax a little and embrace your sexuality and so that he can get help managing his expectations, learning to make you feel sexy, and communicating his wants and needs. It might go a long way to getting both of you on the same page and may even cure his ED.