>>/3568/
 >>/3569/
It seems when you try to "visualize" you are actually entering a "thought stream". Visualization is like a a "calm clean pound" and as you "make some holes on the dry ground" you connect it with the "water" to fill it up and they will slowly "fill up" the form of that hole you dug up. 
This is the "basic" version. Aka the "beginner practice". Now it seems you are already at the part when you "enter the stream". The "stream" is a little complicated because it contains your memories and some sort of "egregoric" memories that your memories "originate from".
So if I go back to the "pond example" I can explain it that you are making a hole on the "shore" and you want it to be "filled up" then you connect it with the "river". While a pond is "slow" and "stationary" the river is "flowing" constantly. So when the hole is "filled up" it also gets "washed over" then because the river is full with "garbage" you notice things that it washes "ashore" then it usually gets "washed away". Because the thought stream is "potent" it feels real but because you cannot "hold it" because it "flows constantly" while you are in one place all the time.

You need not to "visualize" in the "beginner way" but instead understand how your "thought stream" works.

Instead of trying to "actively" visualize something ask it to "take form on it's own" and try to "feel" what is that "morphs it".

When I want to "visualize my room" I am not actually trying to "Paint an image in my head" but asking my mind to "remember it" and as it "takes image" I can "move in it".


Dunno if this helps because you are not at the "beginner level" anymore and my visualization evolved not from "practice" but from constantly daydreaming... not to mention if I hold an image in my head too long it starts making changes in reality... 
It's really a complicated topic because thoughts have a sort of "materia" which affects it's "realness". 

Maybe the advice you need is to learn to "clean your mind" and "cleanse your environment" and find the "stillness of your mind".
...
I am actually bad at doing the advice I just gave. My "trick" is being faster than the "stream" itself or holding the image strong enough that it cannot "depart" anymore... 

You have some weird ass mental block that you will overcome easily when you figure out what it is. I don't know what else I should say. I know what you mean because most of us were at the stage where you are currently but the next steps happen either naturally or with some spiritual practice.