Suffering from anxiety disorder. Case.

Hello! Respected Sir/ Madam I'm 35 year old man since 8 years have been suffering from Non-epileptic [till now 5 times in long intervals] Seizures, anxiety disorder including psychosomatic complications. So earlier some years I used to take phenytoin 100mg twice in day but there was plenty of side effects such as vitamin d deficiency, skin problem & flu like symptoms, but later on doctor switched to levipil500 (levetiracetam) twice in a day, alas! afterthat other complications got worse such as psychosis, fear, mood swings, upset stomach,constipation etc, but when again doctor told me re-continue with phenytoin so after continuing this nowdays side effects are much severe including gastritis,  weakness, sleeplessness etc , but the shocking thing is  when I'm stopping drug while during changing drugs i feel much better fit & fine , and whenever taking medicines developing such problems.Please suggest what should i do I'm too much in trouble and can gabapentin be suitable in this case.