Ugh. Not good! I have systemic lupus (and fibromyalgia, hypothyroid, etc, etc, etc) and take *alot* of medication. However, I've never had any major changes in my hair caused from medication, pregnancy, etc. My hair didn't get curly until I hit puberty. My dad's didn't curl until he was in his early 20s.
I was dx'd at 19 but didn't start a lot of meds until 22 or so. I have had times where my hair isn't has good as it should be but never to the extent of going straight.
I hope the Neurontin is working (it's used in fibromyalgia patients also) amd that your curls return to "normal"