"Damage" is not quite the word, I believe. But that it messed with your brain function, it did. All psychiatrical meds do, in their own way. Antipsychotics are just big offenders, because they mess so much, with so much stuff.
Medications usually either increase the ammount of certain neurotransmitters in certain receptors, or decrease it.
For not receiving the appropriate ammount of neurotransmitters or receiving too much, now your brain has a completely different receptor make up it had before Seroquel.
If you flood receptors with a lot of neurotransmitters, or make them just overstimulated with them with whichever mechanism, the brain tries to "level" things by decreasing the ammount of receptors. This makes you less able to receive stimulation in that receptor. The inverse also happens: If you never get enough neurotransmitters in a receptor, the brain tries to level things by increasing the number of receptors. This makes you way too stimulated to the neurotransmitters the affect that receptor.
There are many different receptor types, that interact with their appropriate neurotransmitters. Depending where they are, they do different things in the body (they're not just in the brain).
Neurotransmitters move through the body, and serve as signaling for the receptor to signal other stuff in the body to do it's functions. Lock and key, fuel and engine.
Since Seroquel mainly (if I remember correctly) DECREASE dopamine, histamine and (some)serotonin receptors, while INCREASE (some)serotonin and norpepinephrine receptors, you're probably quite messed up right now.

Because those are a lot of different things for the body to fix now that it is working without the medication in your body. It just doesn't know how to quite make things work like it used to, or in the just right ammount/manner.
Anyways, now that you know how it works, let me try to help by giving insight to your current "symptoms".
I don't think you are psychotic. Honestly, you are A HELL LOT LIKE I WAS after coming off Geodon (another antipsychotic, which I also took without being psychotic or bipolar, or anything serious).
Reading your description just schocked me, our symptoms after coming off are nearly identical. I am genuinely angry at psychiatrists right now.
To me, you are describing intense anxiety, ADD-like symptoms, obsessional thinking and difficulty having a focused mind. It's like you are somewhat "trapped" inside a very restless mind, full of internal, intense thoughts, fueled by fear and worry, that just can't pick what to discard and what to keep in a rational manner, right? Worrying too much, feeling like certain details that truly are pointless take over your mind irrationally... Reviewing, analyzing, testing, imagining it, running over and over in your mind, telling the same things to the thoughts, telling the same things to yourself about the thoughts. Then out of the blue, it starts again. Rinse and repeat.
If you want to actually go deeper into talking about this, I would appreciate it. Shoot me a PM if you do.
For years I've been trying to explain how I feel to psychiatrists... They never believe it was the meds, and they keep trying to place it under diagnose criteria.
Man, I felt exactly like this for years after Geodon. Still do.
Anyways, took me a long time to recover from this, and I'm not 100%. Heck, not 60%.
But don't worry, it isn't psychosis. IT IS BELIEVED at least, that in my case, it is "pure O" OCD. Purely obsessional, withouht compulsions. You have the repetitive thoughts in your mind, and crazy worry, but no need to associate them with anything tangible.
You know what worked best for me? Lithium. Lithium is a very safe, very effective and damage-free medication (unless your kidneys are not that good). And it's specially good at repairing the brain to it's best shape, since it evokes neurogenesis like no other thing.
It also shoots serotonin to the hippocampus, amongst other technical goodies, which helps obsessions a lot. But aside from helping the brain repair itself, it helps calm down the mind (prepare to get even less intelligent, though with less "clutter"). So it's a way to fix in the long term, and also to treat the symptoms.
Don't worry man, you're not psychotic. You just had Seroquel get dopamine and serotonin out of whack, and now parts of your brain just can't work right... but not psychotic or anything THAT serious. Just anxiety and obsessional thinking.
If you wanna get serious about fixing yourself, you should learn about neurotransmitters, receptors and the medication, supplements or whatever that work on them.
Let me try to help with medication that I know it works for me or other people:
To me, lithium is the base of the treatment. It holds everything in place, so to speak. Never too low, never too high. Calms my mind greatly, makes my mood better, helps me shift attention on command and shuts down the automatic obsessive thoughts like no other medication.
Then I work on serotonin. Serotonin is the main thing you want to get UP if you want to treat obsessions. I particularly think SSRIs and SNRIs (Citalopram, Escitalopram, Fluoxetine, Sertraline, Venlafaxine, Duloxetine, Paroxetine, Fluvoxamine) are absolute garbage. Nasty side effects, too much apathy and dulling while you take them, and rarely help on the long term. Not to mention withdrawals of their own.
I enjoyed tianeptine (Stablon) the most from all antidepressants I took, to help with obsessive thinking. Really calms down the mind and I feel much better upon cessing treatment. People say a lot of good things from slow releasing trazodone, as well. I never took it for long, though, to say personally if it works. But it increases serotonin a lot. People speak very highly of Anafranil (clomipramine), a tricyclic antidepressant that is the ultimate weapon against OCD. I never took it, due to sheer fear of the side effects and possibility to mess with your heart (TCAs are old antidepressants that are used as a last resort due to their dangerous, possibily-fatal side effects. But their effectiveness is unmatched to this day).
Currently, I take tianeptine every now and then only (it's a drug that works immediately), but take 300mgs of 5-HTP everyday. 5-HTP has been amazing for mood and the thoughts. 5-HTP is actual serotonin, you take in powder form. You can buy it on iHerb.com or any other supplement store or drug store. It helps me a lot.
It's funny, but dopamine also needs to be increased in my case. BUT JUST IN THE RIGHT AMMOUNT...
Obsessions and paranoia are created by excessive dopamine mostly, in certain areas of the brain. Seroquel's main action is to decrease dopamine, so when you took Seroquel off, your brain was just too sensitive to your normal levels of dopamine (less neurotransmitters, more receptors, as I said at the beginning of this), making you think too much, obsess, have too much mental energy going to all the wrong places, have a lot of anxiety, etc.. Anyways, it's my theory. For me, i can't increase dopamine much. It worsens anxiety and obsessions. But just the right ammount is great to feel actually more focused on EXTERIOR STUFF, INSTEAD OF JUST OBSESSING INTERNALLY ALL THE TIME. You can try stimulants (Adderal, Ritalin, dexedrine, etc..), bupropion, or like I do, take l-tyrosine. l-tyrosine is much like 5-HTP, an aminoacid that is converted to neurotransmitters in your body. l-tyrosine becomes dopamine, and the body then decides by itself what to do with this extra dopamine, unlike a med that would just shoot dopamine everywhere in a killing spree of neurons.
Anyways, hope I can help. Your symptoms are so much like mine, and for the very same cause, that I literally wish we could work together in this.