Adelaide,I think at he beginning mostly all of us experience some discomfort and changes in mood with the medications and specially with our condition.
I'm on gabapentin for a while but I can't keep the same dosage everyday,normally by my dr advice I take it as tolerated,the goal is for me 1800 mg daily plus other meds.
I think in my case that did not influence my mood but when I got my spinal cord stimulator,everything changed .we had to work hard to reprogram and get the signal away from my pelvis and abdomen,it was directed for my right foot and ankle,but like Bram said,stress is also a key factor to be no in the mood.
One of my colleague to happens to be a pharmacist recommended me meditation ,yes meditation and relaxation with focus on breathing,to me was like whatever they had no idea what I meant but one night i was so tired to non be able to concentrated in anything, I google meditation techniques in general and found at music help relax your nerves and calm your pain by focusing on your breathing and isolate everything else,so I found in you tube the perfect music for that relaxation part,Tibetan singing bowls,I started to listened real low at the beginning every night ,my husband is been real patient on that matter as well as yours ,but been relax changed the mood,I think medications affect your body,but stress affect your brain more,try to relax and find something that keep your mind away from the pain,like Bram mentioned,oils,massages ,anything that distract your mind from the pain,hope you find that point of relaxation,yes I did not believe on it either but works after a while,but works .
Hope you the best and always check with your dr,there are so many things to ask,just make sure,do a list and ask all kind of questions and relax,wish you good luck,Jesika