Hard to Tell

*sorry this is long I just want to give as much info as I can for more feedback*

Hey everyone, just a little bit about me I am a 23 year old fit male in medical school with a history of porn/masturbation since the 7th grade. However, I would love to reboot with no masturbation or porn. I have a incredibly sexy girlfriend with a high sex drive however sometimes during coitus I am not 100% hard (instances where she is on top or when we have a brief (15 -20sec) pause between position changes) or I start to go limp. Now in the past I have experienced psychological blocks and feel as if I still do today which I believe may be preventing me from being fully aroused. I know if I think about if I am going to be 100% erect or even feel it slightly diminishing, I pretty much will lose the erection or something close to it. I have also had times where I received head and just didnt feel anything but if I got 3-7 days without porn or masturbating;as expected I can feel it better however I have gone a whole month with out PM and it still felt the same as a short break from PM. I mainly watch porn when Im bored at home alone and never feel like I have to watch it when Im with my friends or girlfriend. (so in essence if I always was out of the house I would never watch porn)

I have noticed that after orgasm it becomes much harder to have another and requires slightly more work to get an erection again (pretty much needs constant physical touch). This really bothers me because I cant pinpoint whether or not my varying erection issues are from PM or arousal issues, psychological etc. I should note that I take pride in how I perform in bed but that's because I like to perform well in pretty much everything I do. I used to be proud of the fact that I could last quite a while in bed but now I am realizing its "work"(rough and fast sex) especially if we are going for multiples rounds that day for me orgasm and rarely will I Orgasm from slow sex (have to be super in the mood). This fast and rough sort of mimics how I masturb while I was younger which mostly Dry fast and hard JO. It wasn't until a year ago that I started using lotion or lube after finding out I probably desensitized myself with bad JO habits for years.

I will also add that I used to be extremely turned (erection without touch) on by basic porn such as lesbian porn, women masturbating when I was much younger but as I got older I needed more out of porn and started watching more wild taboo stuff to get it up and wondering if that also plays a role in my arousal levels during real sex. Physically, I am in good shape work out 4x a week with cardio so there should be issues there.

I guess my question is, if its normal for guys erection to diminish at different times during sex or are you completely hard the entire time even with out some form of physical touch? Also are my problems stemming from desensitization, Arousal, psychological blocks, porn, masturbation? Any input from you guys/girls would be helpful as I just want a normal PM free life where I am completely present with my girlfriend without any worry/distraction of my erection.