I've had tinnitus and sensation of fullness in bith ears for a year now but my ent doctor took one look and said theyre fine, what could be causing it?

Many causes: Tinnitus is actually a very complex perception of some type of noise or sound in the ears or head. There can be many causes and hopefully your otolaryngologist did a hearing test as part of the evaluation. Common causes include wax in ears, fluid in middle ear(from cold/allergy), hearing loss, and tmj/clenching/grinding problems. This last one often gets overlooked and is a common cause.