I went to the physical therapist yesterday that my ENT prescribed. He diagnosed me with this exact issue. He said I was a classic case of tinnitus caused by C1 and C2 misalignment from bad posture over years. He has assigned me to correct my posture. That was yesterday. So I will see what happens.
I can go from no tinnitus to severe tinnitus to mild tinnitus. All in one day. He said this is not random and that I was lucky I was sent to him as he is one of the few people that does what he does in the country. He said most ENTs don't send people to doctors like him because it's not profitable and the science isn't on the forefront of most ENTs minds after they work for 20 years. They are just following the motions.