I've Been Taking 1500mg Of Methocarbamol And 600mg Of Gabapentin

I've been taking 1500mg of methocarbamol and 600mg of gabapentin for approx. 2 years. The meds were prescribed because of issues having to do with headaches & eye pressure. I had neck surgery in July of 2017 because of issues with me neck and head (bad headaches and a lot of eye pressure)). I also had a nerve block to the left side of my head 3 weeks ago. My continuing problem is that I feel weak and physically wiped out. Are the drugs causing this?