You're not stupid. I think most people, when told to "visualize" something, close their eyes and can see an image. It may not be 100% clear, but its closer to what you might see when you dream (If you can see your dreams). It might be fuzzy or out of focus or lacking detail. My step-daughter is on the opposite side of the spectrum from me, where she is HyperPhantasic and I have absolutely nothing if I close my eyes and try and imagine something. She says she can picture something in front of her and move it around with her mind like Tony Stark does in the Marvel movies. For me, again, I have nothing. I can tell you what something is or looks like, but I don't see or picture anything. I like to say most people have search engines for thinking of things and I'm using a filing cabinet.

I've had the same thoughts. My understanding is that what you're describing as your experience is exactly aphantasia. We can think about something, and because we have actual knowledge of what it looks like in the world, we can speak about what it would look like, but in our minds we cannot actually see it. The most aphantasic answer choice on the assessment offered on this site is, "No image at all, you only know you are thinking about the object." So you can try to imagine a table you want to design and say, "Well, my table would be brown with carved legs and rounded corners," because that's what you are thinking that you want, and that's completely consistent with aphantasia. If you can't actually see an image, that's what defines aphantasia. For me, filling in the details of exactly what shade of brown or how the legs would be carved is harder. I design floor plans as a hobby and kind of know what I want when I start, but that comes from my knowledge and imagination, not a mental image. I work out the details by erasing and redrawing until I get something I'm satisfied with. You're not stupid either. It's pretty crazy to ask if and affirm that your brain doesn't work like 95% of people's without a doctor telling you, so it's natural to second guess.

I have been very confused in the last few days too. When I closed my eye, I see nothing but a black fuzzy screen, but I can think of something, but can only add things if I try to add things. I don’t know if that counted as “seeing” or not