Question: Ringing in both ears…but specialist sees nothing wrong

I’ve had a prolonged ringing in my ears for about 8/9 months now. It’s simply a high pitched ring, no pain, no other symptoms. It’s much stronger in my left ear than my right. I don’t go to loud concerts or in any way expose myself to any other extremely loud events or circumstances. It really bothers me, gives me headaches from time to time, and makes it hard to relax or fall asleep at night. It comes and goes as it pleases, sometimes it’s louder, other times it’s quieter that I can barely hear it but I do not recall it going away completely during this period of time. I do not remember when it started exactly either. Possibly during the cold winter? I am from Calgary, Canada. I’ve seen the best specialist in town about 5 months ago, he didn’t see anything wrong, checked my hearing and it was perfect, so he sent me to get an MRI done. My appointment for the MRI is still not for another 3 months. Would really appreciate any insights. Thank you very much.