Dilantin and lack of motivation

I've been on Dilantin for approx. 5 years now because I began having seizures after being involved in an airplane crash when I was 14. I suffered a ABI (Aquired Brain Injury) which has had a considerable effect on me. A considerable problem with this is trying to separate what symptoms are a result of what condition.
Since I've been taking Dilantin - I've noticed first of all my gums tend to be a little more sensitive than normal, bleeding at times when I brush.
My ability to learn new activities & study is also diminished, I find I have to study twice as hard & have to do things twice as much as the average person before it finally "sinks in". To the un-trained eye, this can be easily mistaken for laziness or lack of motivation. I had always attributed these learning difficulties to my brain injury, but after looking into Dilantin side-effects, I've discovered that diminished learning has also been associated with taking this drug.
Another side-effect I've noticed is a diminished sex-drive. Only recently have I started looking into this, but I've dealt with this for the past couple of years, and it has really started to have an effect on my relationship with my wife.