Gabapentin is a fairly mild drug, except that taking it consistently for sleep and suddenly stopping taking it can easily mess up any sort of sleep you had going before.

I was given gabapentin for ptsd sleep issues and it really did not do anything for me either. My pdoc later prescribed me Prazosin for ptsd nightmares and that helped some. It's a blood pressure medication, but helps with calming you down at night and keeping the nightmares a little more mild. I mean, I never had insomnia, just horribly vivid nightmares, so I don't know if it will be exactly the same. It might be worth asking about though.

Good luck with everything! Keep pressing through and don't beat yourself up when things get too hard.