Since you say your relatively young I doubt it's anything physical. I will strongly agree that if you're a big consumer of porn and you jerk off a lot, let it go!!! But that's secondary to your real issue, IMHO.
I suspect the real issue is PA. You note in your OP how sexy and attractive the ATF is and you note here how you "reinforce" to the lady how beautiful and attractive she is. This happened to me once. I had an ATF that was absolutely an 11 to me. Per my standards she was perfect. Hence, doing the deed was often times problematic for me. This was the first time this had happen to me with a lady I wanted to be with. Sure it's happened before with ladies who, in the end and once we hit the sheets, just didn't do it for me so that was understandable. But never with a women that had the total package and/or I was completely attracted to.
Bottom line, I was intimidated by her beauty, intelligence, her total package and it fucked with my mind. I even did experiments where on the very next day after seeing her I would see another ATF on the list and all would work well. So it was not physical it was allll mental.
I'm probably older than you as I will be 54 VERY SOON. I will admit my dick does not get hard just when the wind blows like it use too, nor can I blow out two shots in an hour on a regular basis like the old days. The refractory period is simply longer now. NOTE: they are testing a drug now that may eliminate the refractory period. Now that's the drug I'm waiting for. I have outgrown the need to cum for the sake of cumming. I now prefer the journey over the destination. Hence, I now tend to book longer sessions 90 min to 3 hours, if there is a vibe with the provider, then MSOG is not a problem. But I digress.
I would add to the suggestions made that you not place your ATF on a physical or whatever other "pedestal" you may be placing her. This inhibits performance in some cases. Relax, enjoy her beauty and presence. What helped me was honest communication with the lady and she even initiated it. Apparently dudes before me had experienced PA with her and she recognized the symptoms. During one session she simply said, "...relax and enjoy the ride.." She proceeded to apply her anti PA routines and over time all was good again.
The mind is the best Viagra or, ED we have.