I am surprised you don’t mention an SSRI in your list of medications. Anxiety and depression go hand in hand and in my humble opinion gabapentin does absolutely nothing to address anxiety or depression. It has been around forever and is prescribed for just about anything under the sun.
Try a good SSRI like Zoloft that is well tolerated by most people and combine it with Wellbutrin. They are very complementary. I also take Buspar and Klonopin. I have been taking the same dose for over 35 years and the combination has served me well.
Best of luck to you.