I'm in the same boat. No visual imagery but I do "see" abstract relationships and how they interact. I'm reminded of a case where a man had head trauma-induced blindness. He couldn't see colors, shapes, etc. But it turned out he could still see motion. He described it as black moving on top of black. It's sort of like that, somehow I experience the contours of the abstract relationships, but they feel very insubstantial.