Hey
@Byzek
As drugs go, Quetiapine (Seroquel) is pretty well-tolerated and is thus considered safe. There are a lot of people who use Quetiapine as a sleep-aid without issues, as it is effective for this purpose, but it can cause side-effects. Quetiapine is an antipsychotic drug, as it's useful for controlling symptoms of psychosis, but this typically means a higher dosage than what would be used just for insomnia. A typical dose for insomnia is going to start at 25mg-50mg Quetiapine and most people find this to be plenty, whereas dosages for antipsychotic symptoms go into the 100's of milligrams.
Antipsychotics are known for their ability to "slow down" or "sedate" psychotic patients. Patients often describe this as a blunting of their emotions or imagination, so it's not strange for you to experience this "flatness" that you're describing. If the drug is not working for you due to these symptoms, I would suggest trying something else, but these effects don't indicate anything medically dangerous.