try to lower the dose, seroquel
is used as sleeping aid at around 25 to 100mg approximately. You can try some antidepressant to control your appetite.
I definitely do not recommend ambien or lunesta, for long term treatment of insomnia. They have a very short life in your body and it which builds up tolerance quickly. The so called "z" drugs ambien and lunesta (zolpidem, zopiclone, zaleplon and eszopiclone) are for short term insomnia only.