Can you get an erection alone watching porn? Can you get erected with porn without phisical stimulation?
I am not a doctor but I am experiencing ED at 66 due to an enlarged prostate, which is quite common at my age.
I urge you to see a family doctor, and ask for a referral to a urologist. Only a urologist is qualified to diagnose your problem.
If you have a problem with your parents (e.g., driving you to the doctor or asking questions, respond by saying "I know you are concerned about me going to a doctor because you love me. This isn't a serious issue but it bothers me. I'm not telling you about the details because it's private & a bit embarrassing. I ask you to respect that and not further embarrass me by asking any more questions. If it DOES turn out to be even slightly serious, I promise I'll tell Dad (or you)." If it's Dad who's asking the questions, just tell him the exact same thing. If you DO have to tell them, you can leave out the girlfriend part and just say "I get turned on sometimes but don't get erections, and I'm worried about it. My friends don't seem to have trouble getting them. What happens when I (eventually) get a girlfriend and we decide to have safe sex?" I put the word "eventually" in parentheses because that really is a lie, and if you want them to trust you, you have to be trustworthy to them. I added "safe" sex because that will reassure them you're being responsible, & because that what you should be:responsible. See below.
If any doctor blows you off by belittling the problem or giving you a lecture, don't bother trying to argue with him/her. Get another doctor. That's lifelong advice.
If either doctor is a woman, pretend she's a man and tell her everything. Remember that she too dated and usually had sex while dating. If you are REALLY uncomfortable, tell her you're embarrassed because she's a woman. Assuming she's a good doctor, she'll understand and try hard to put you at ease.
Finally, you really need to man up and be responsible with your (any) girlfriend. WEAR A CONDOM. You don't want to get her pregnant. Also, as you and your girlfriends get older, remember that from a disease point of view, you aren't just having sex with her, you're having sex with everyone she's ever had sex with, and all the people her boyfriends ever had sex with. In particular, remember that herpes is often difficult for a woman to detect. If you get it, it's a lifelong problem for you and any woman who might want to have sex with you. I could tell you terribly sad stories about this rxact situation. ☹️
Good luck, and don't quit until you get a satisfactory answer from a urologist.
I had the same thing happen to me. Had a girl I was comfortable with, broke up before college, then a few months after I realized I might have an issue, couldn’t masterbuate or it would take forever. Took cialis for a bit and my EQ improved, L Argine helped get blood flow back. I hurt my back and had a lil nerve damage (based on shooting pain) so I thought it was physical but I think it turned out to be mental. Dealing with your emotions and any insecurities you might have abs basically relaxing might help. I didn’t even think I was stressed at the time but eventually I understood so just know you will be good. The more you focus and worry on it the more you let it control you