I've been on Gabapentin for 6 months. I started with one 300mg/day, then went to two 300mg/day after 2 weeks. After another 4 weeks we bumped it up to 3 a day. I've stayed with that dose. I don't feel as though I have any side effects. Maybe very slight drowsiness but the fibro keeps me so tired that it doesn't make a difference.
If you try the magnesium make sure you take it with malic acid. I've read one of them by itself doesn't help.
This combo (gabapentin and mag/malic acid) has really improved both pain and fatique for me. Which has improved my mood. My dad commented today how much better I've sounded lately. This coming week will be a test for me - first full 5-day work week since starting mag/malic combo. Hoping my energy stays up. I'm also learning to pace myself to conserve energy and to manage stress (have more pain and muscle tightness then).
I think there is a link to the "spoon" explanation in Fibro 101. This helped me to not only explain it to others but to understand it for myself. Take a minute to read that.
This is what is working for me. Don't worry, there will be ups and downs but you'll find the right treatments for you.