I know exactly how you feel fearing a return to bad times. I was at my very worst two years ago and tried antidepressants with no success - just terrible side effects. Sleeping tablets just give me two hours of sleep - why I just do not know. I despair because of my poor sleep. The last two years especially have been bad news as I can no longer work (as a teacher) because of this problem.
My insomnia seems not the same as yours. I mostly manage to get off to sleep but then I wake up several times during the night eventually waking after a heavy hour or so of sleep in the morning feeling terrible with a thick muzzy head. This, at worst, leads to anxiety and depression but, thankfully, the depression at least is keeping away a little for now.
I always know when I will get to sleep as I find the bed feels very comfy and I get to the stage where I forget the thought my mind was working through (I'm always working through some nonsense or other - hardly ever worries, just this or that). When I am about to fall asleep, behind my closed eyes, I see a mixture of colours and the next thing I know, I'm asleep.
When I took mirtazapine it seemed very good at first for sleep but I still woke feeling awful. The useful effects on sleep soon wore off, though, and in the end I felt I was wasting my time taking them.
I went to a sleep clinic and was recommended a self-help book. Here's a link, it might help (it didn't help me but is highly thought of):
http://www.amazon.co.uk/Overcoming-Inso ... 58&sr=8-11