Psychological ED as a teenager about half of the time

Hello people of Reddit. Without getting too specific, I am a teenager who tends to get what I only assume is psychological E.D about every other time I makeout and have sex with my girlfriend. Some days I get hard as soon as we start making out, and can even go 2-3 rounds of sex the whole night. However, some nights it’s a struggle to get hard even after much foreplay. I am very turned on and attracted to her, and this still happens on these random nights. I get random boners everyday, morning wood, etcetera so I know it’s probably not a physical problem. I am also in very good shape, exercise daily, and eat pretty clean which also points to the fact that it’s probably not physical. I usually masturbate about every other day of the week, but I am starting to cut that out. It has been happening about 50% of the time for the last month. I am looking for any advice, because this is very frustrating and disappointing for me.

EDIT: I forgot to mention that I also get in my head a lot about not being able to get a boner and think about it before we hang out and while we’re making out (Performace anxiety?) and this could def be the cause… I’m not sure tho.