Seroquel and other meds combo. Dangerous?

I used to take Seroquel 200 but had been weaned down to 25 mgs. In addition to the 25 mgs, I take 1 mg of Xanax, 10 mgs of Ambien and a 30 mg of Melatonin each evening before bed. If I take the larger dose of Seroquel, I tend to gain weight but now I am concerned about the combination. My physician doesn't seem to be concerned but Im hearing too much about these high profile people dying at a young age from a combination of medications similar to these. Not to mention, I have been falling asleep very quickly, almost comatose, for a couple of hours. Does anyone know if this is a dangerous combo and what I should suggest to my Doctor who seems to feel this is okay? Im taking all of the above mentioned medications for sleep ( insomnia ) not depression or anything else. I like the quick results, don't have any lasting side effects or problems but again, I cant help but question the combination. Also, many people who I talk to ( who are not in the medical field ) feel this may be a dangerous combination. Please assist. Thanks