Tinnitus is a symptom related to many medical conditions. It may be intermittent(have it certain days and certain days not) or an annoying continuous sound from low to high pitched ringing as in your case.The most important consideration is to determine the main cause for tinnitus. High or low blood pressure, heart problems, circulation problems, exposure to loud noise, head and neck injury, medications, cigarettes, and alcohol can provoke this symptom. Current treatment with gabapentin is probably causal therapy of a medical condition that causes tinitus.You might consider a visit to a specialist like a neurologist or an otolaringologist for further consultation.