After only three days you should not have any problems that are related to the Trazadone. It has long since been eliminated from your body. Only after LONG TERM use would you need to be concerned.
I suggest you revisit your doctor and disuss this in more depth. There are many less potent drugs out there for insomnia. If insomnia is your ONLY issue, before going the pharmaceutical route, why not talk to your local health food expert and see if a natural remedy might not work? It certainly will not hurt.
You say you are feeling "nervous and anxious," is this due to lack of sleep, concern about the Trazadone, or do you feel there are other issues involved?
Two questions I'd ask my doctor if insomnia WAS my only problem: "Why put me on an anti-depressant for insomnia and especially one which has known side effects of stimulation and insomnia?"
No doubt those partiular side effects would go away in time, but it still seems like an anti-depressant is overkill for insomnia.
Which is, of course, my humble and non-medical opinion.
Peace
Greenlydia