Neurontin and stomach problems

I started dating a guy that takes neurontin, thus the reason I am researching this drug. He is taking it for mood swings and a.d.d. He doesn't take it constitently. He takes various doses depending on the circumstances (sometimes he takes it like a party drug and he drinks). I can tell right away when he has taken a higher dose. He is lethargic, he drools, he is off balance, and actually seems somewhat slow (mildly retarded). I know he is intellegent, however, this drug is making him into a person that he should not want to be. I don't know if I can continue a relationship with someone that seems to be drugging himself to a complete stupor.
He said he was going to cut down to one pill, three times a day, however, I think he is having a very difficult time doing that. He is very addicted to his MEDS as he calls them. This drug seems to be destroying his life and he doesn't even know it.
He continually has to urinate, has a low sex drive and he experiences stomach problems along with back problems. This is the only drug that he takes. After what I have seen I wouldn't prescribe this to my worst enemy.