Since you are normal in one eye, that one is not a worry today. Worrying is unproductive and it also leads to stress which is a health risk in itself. So you should focus on other things since there is nothing that can you can do to affect the good eye. It is a very good idea to remain blocked from that site because you do not have a problem and you likely have a long life ahead of you so live it to the fullest as best you can.
With the eye you have a reason to be concerned, as you've had eye problems. But you also appear to state it's not just about the eye, that it's also about other things too, even a common headache. If I've got this right, that this is something more than the eye, it might not be a bad idea to see a therapist about it. I would guess that you might be reacting to the things you've gone through, which would be a common thing but not one you'd want to live with forever. When something happens to you and it seems to be causing phobias or fear that gets in your way, it can be very productive to talk it out with a professional. It's harder when you have no idea where the concern is coming from. There are things you can do prophylactically for the good idea, by the way -- there are foods that are high in the antioxidants that protect the eye. There are supplements that contain those substances as well, though you're pretty young for that. My wife is in her sixties now, but she had eye problems in her youth and surgery and it took away a lot of her peripheral vision. She doesn't sit around and worry about it or other aspects of her health, she's almost abnormally sane, but she has always had a phobia about driving because of it. She can drive, she's just too fearful she might not be seeing everything. I've tried to teach her how to drive in a way that will work for her because, really, you most need to see only large things when you drive, you really don't need to see the small things she might have trouble with -- it's not going to be a problem if she runs into a fly -- but this is something that has lingered. Because she is so sane she just gets around in other ways but in your case you're worrying about it. This can become a bad habit and get in your way. That's why I say, if it's spread beyond the completely understandable eye concern, get over it now when you're young and adaptable. If it's just the eye, really, we all have something we worry about too much. As far as the protection for you good eye, you can research this. Glutathione, found in wheat grass, is the most important antioxidant protecting the eye (also the liver). Lutein, found in green veggies, protects the eye. So there are things you can do that might help.
I have a dear friend whose son was born at 23 weeks too! Wow! He's a teen now as well and he has had constant monitoring of his eyes. He's had two surgeries as well and is checked every year for changes that would indicate more intervention being necessary. Extreme preemies do often have eye trouble. My friend's son is seen by a specialist once every single year to monitor for changes which is pretty common for preemies such as yourself. Is this what the eye appointment was for 3 months ago? Most children's hospitals have someone that is excellent at this and it is good to be followed consistently over time by the same eye doctor. But regardless, you were just checked and all is fine. There's no indication that this has changed other than your own anxiety.
Your fear is not totally baseless with all you have been through and the issues with eyes in extremely premature babies. But it is usually correctible. So, keep that in mind! But you don't want to live in a well of worry! Are there other things that you are anxious about? How is school going? Any other repercussions from your early birth story such as learning differences? That's also pretty common and in the teen years at 15 it probably can all feel a little overwhelming. It's important to ask for help. A therapist can talk about coping strategies with you.
So, hang in there. You've had a long road and sound like you are an intelligent kid doing awesome!