Medications work differently in each person, and it takes considerable time to determine in any particular case whether a given drug and the certain dosage is effective at all.
Many doctors state that patients should not expect full stabilization for at least 3-4 weeks.
Depression does not respond instantaneously to resumed medication, typically taking up to 6 weeks to respond.
Mania may disappear slowly, or it may become depression.
Lamotrigine, as a mood stabilizing drug, is more effective at treating or preventing manic episodes, but, due to its antidepressant potency, it is helpful in treating depression in bipolar patients, too.
You may experience the effect of this drug in a week or it'll take a month to kick in.
Lamictal can start to work in as little as a week but will not reach full efficacy for about 3-4 weeks. Most people report that it works well to manage their bipolar episodes. Hope you feel better soon.