You said you were feeling good on 100mg of Zoloft. Why did your doctor increase your dosage? I'm on a low dosage of Lexapro (no side effects other than weight gain) and I told my doctor that I'd like to stay at this dosage and see if I stay on an even keel (which I have).
As far as insomnia, are you getting regular vigorous exercise? I've been trying to exercise daily and have found that it really helps with sleep. Also, going to sleep at the same time each night and not watching and TV (or other electronics like smartphones) at least 30 minutes before bedtime also has been proven in studies to help sleep. Something about lighted screens put our brains into an active state that doesn't wear off immediately.
I have never taken gabapentin. What is it that you don't like about it? There are other medications for sleep that you could try. I take klonopin for sleep but that is habit forming and I'm certain after all these years I'm hooked on it so I'm not advocating this drug in particular but just saying there may be other medications for sleep that may work better for you. JGF
Unfortunately when the dosage is increased, the side effects come back and you are back at waiting another 4 weeks for the dosage to build up in your system. :( I know that stinks but it happens. It happened to me when I went from 150 to 300 of Wellbutrin. Hang in there. You are doing what you need to do to get better!