I'm so sorry Adalaide, that is one side-effect no one wants...
I know a lot of folk on this forum are on gabapentin and it works very well for them, but it's not right for others. I went on to gabapentin myself a while ago, and had to come off it because it wrecked my stomach. But....big but, I noticed a change in that side of my life as well, things just weren't the same, and I definitely wasn't sorry to be off the stuff. I was on lyrica before it at a high dose, and went on to gabapentin because my GP thought I'd have fewer side-effects (plus I suspect the fact that lyrica is expensive had a bearing on his thinking

). What a joke. I came off the gabapentin very quickly simply because i was being so violently ill that i couldn't keep anything down, and after a week off everything I went back on to lyrica again at a low dose (50mg twice a day). It now does more than the gabapentin ever did (which was sod all), and I have pretty much zero side-effects. The lyrica is more effective for me at a low dose than it was up high. Odd.
As Heidi said, ring your doc ASAP, and ask her opinion. Meds are a very personal thing, and each one of us has to find the right mix for them. I can only give you my experience and opinion. My pain doc said gabapentin was 'nasty stuff' after I'd come off it... Which coming from discussions about opioids and other strong stuff, hit home. You will find something that works for you, never give up on it. The search can be tough though...
I understand your fear and distress completely. It's horrific when you feel like this disease might take something so precious away, on top of everything else it has affected. Try not to panic. That side of things sorted out pretty quickly once I was off it, and I've been fine since thank goodness.
I have my fingers crossed that this is unconnected and a temporary issue for you. Sometimes stress and other factors can affect that side of your life more than you think.
Take care of yourself, try not to worry, and let us know how you get on with your doc.
Bram