Great that you feel better.
Medications can be tricky. They may be approved to treat certain condition, but during the years of development be noticed to improve something else as well and the physician has the liberty to treat you as he sees fit. While working in the pharmaceutical industry I knew of one compound that was developed for the treatment of depression and be found along the way to be excellent for the treatment of psoriasis, improving the life of thousands of patients.
Gabapentin is one of those miracle drugs that can help in many problems. Real antidepressants take a real long time to help.
I am very curious as of what your DH said.