Is it ok to raise the dose of lamotrigine by 25 mg each week, given that 4 years ago (during my first trial of it), i was following the standard dose-raising practice (by 25 mg every 2 weeks) and never had any side effects let alone developed a rash?

Lamotrigine: Dosage schedule and escalation of dose is different when used in seizure disorders compared with bipolar disorder. Most general practitioners don't have enough experience with this medication and defer it's use to specialists who use it often. Don't make dosage decisions without supervision from the prescribing specialist. I'm sure your pharmacist will agree with this advice.