Being in a relationship is really good as you are countering your P use by being wired to a real woman.
You mention not taking this seriously and to be honest, I don't think thats the problem. The problem is addiction. Why? Because high-speed internet porn is such a big reward for your primitive brain. You have to get your fix, and when you don't get it the brain will punish you with disturbing emotions. It makes sense that you want P when you are stressed because the amount of reinforcement you get from P is almost unparalleled. Like Gary says, you hit the "evolutionary jackpot". Why would your brain back away from that? Its not about the porn in itself, but rather how your brain interprets it. Anyway thats the way I understood it.
I think that the first step of beating an addiction is to acknowledge that its an addiction. The illusion of being in control and thinking "I can quit once I get real ED trouble" is, to my ears, the words of the addicted brain.
You shouldn't take my word for it, but as I said, get informed and check if you are actually addicted to using P. I know I had a hard time accepting this in the beginning. Still to this day, almost 5 months clean, sometimes I still feel like I wasn't really addicted and maybe its not so bad etc. This is where my reading up on the subject really pays off. I know the adverse effects and I have also seen at least some of the light at the end of the tunnel.
Looking back on my life P has been there for many years, and I know where that path leads. It leads to no good. You know, I was also in a relationship and thought everything was great, I still used P but not as much. Then one day, my gf wants to break up and guess what my teddybear was? I had "beaten" PIED while in a relationship and having sex without problems, but it quickly went downhill when I got single, and after a while I noticed I couldn't get hard anymore. And even worse, I wasn't even turned on when I was in bed with a woman. That was a really sad time in my life and it has ruined a lot of my love life from there to now.
I'm not making predictions here, but simply trying to make a point. Addiction to P, coupled with its effects on the brain is really something you should think about. Did you know that P numbs the dopamine receptors in your brain, thus making other things less appealing? Maybe you've seen the video, but its very scary stuff. Its like the brain get *numb*.
Long post here, but I hope its of some help or at least makes you think about it. Catch the shit before it hits the fan.