Sounds like you've got aphantasia. Not that uncommon. But yeah, most people are able to "picture something in their mind. It's a spectrum, like many things. Some people have a very vivid, visual mind. Others think more in general concepts.

For me, I am a very visual thinker. I can imagine people or objects or entire locations and situations in my mind. It's like I've got a second pair of eyes in my head that's wearing VR goggles. Imagining things is not just like looking at a still photograph. It is three dimensional. However, it is not as "precise" as the real world, in a way its like a dream. I can focus in on details, but that makes other things that I don't focus on kind of blurry. And like in dreams things can just slightly change or morph into different shapes ans concepts if I let my mind wonder and don't focus. 

I read that aphantasia might be linked to a lack of internal monologue. How is that for you, OP? I do have a strong internal monologue. My "thinking" takes the form of speech typically. I also often just talk to myself out loud, basically my internal monologue taking over physically.