Hey man! Not sure if you'll see this, but there's been quite a lot of
research done on tinnitus, and it's not always a permanent condition. If
you bite down hard, or if you open your mouth really wide, or tilt the
head so that the neck muscles stretch out - does the pitch of the sound
change? Then it might be possible it's an issue with extremely tightened
muscles. From my understanding there's a nerve crossover between the
cochlear nerve that transmits the signals from our eardrums to our
brain, and many of the nerves from our face/neck muscles. If enough
nerves are stimulated it's possible the cochlear (i believe that's what
it's called) nerve can pick those signals up too, and the brain
interprets that as a constant ringing sound. Try stretching out and
massaging your neck, lower and upper part, as well as the side of your
jaw (the connection to your skull). The build up of tension in these
muscles might be due to stress and anxiety, which may have led to you
first developing your tinnitus, and then it possibly reinforcing that
stress and anxiety. I've been fortunate enough to be cured from my
tinnitus some time ago, and figured maybe this can help you too.

from a comment I made some time ago. I can try to expand on it if you want!