The past couple days I have nonstop ringing in my ears. I've had no trauma at all. What could he causing this?

Many things. The most important condition to be evaluated for is sudden sensorineural hearing loss, this would require a visit to your ENT or audiologist. This would require timely treatment. Anything that causes hearing loss such as ear wax, ear infection can also be to blame. The most common cause is hearing loss related to aging. Loud noise exposure can also cause tinnitus as well.
Ringing in ears. The two most common causes of acute ringing in the ears is either allergies or infection which can block up the eustachian tube which causes severe pressure on the middle ear, or trauma, like a severe bump to the head. Other causes include medication (especially aspirin) or airplane flights. Rarer causes include meniere's disease (with vertigo), acoustic tumor, or multiple sclerosis.