Can I go back on Dilantin after being off it for a year?

I was on Dilantin for almost 18 years with great success, but unfortunately it got to the point where my body was eating it up too fast and I was up to 800mg a day, which I agree is getting too high. We had to move to another city with my husbands job, and I'd asked my neurologist in years prior what would ever happen when the day would come if I couldn't take Dilantin anymore because my level was too high. He said I would have to go on something else for a while, then be able to go back on it. Well, that was almost a year ago, and I had to change neurologists and she took me off of the Dilantin and put me on Topamax, which worked great for my seizures and migraines, but was horrible with hair and word loss. I've asked her about going back on Dilantin and she doesn't want to because she says there is too much risk associated with it, i.e liver damage, osteoporosis, etc. She said 800 mg a day is too high, and I explained to her that I didn't start at 800mg, it took me almost 18 years to get there. She still refuses.Now, I'm on Depakote ER which is not working for me because I'm having facial numbness. It's taken me almost 2 months to get off of Topamax. I'm now down to 50mg at night along with 1000mg of Depakote ER. I told her I was not feeling quite right on the 1000 mg and she upped it to 1500mg and it made the facial numbness worse and it made my brain feel like it was being affected in the "good" areas as well. It's terrible going from one medicine to another, up and down. My question is basically, should I get a second opion or is the doctor right? Have I been off of it long enough to go back on it at a reasonable dose? Sometimes I think my neurologist has something against Dilantin or something.. Any advice would be helpful and appreciated.. Thanks