One thing about tinnitus, the more you think about it, concentrate on it or have anxiety about it the worse it will get. I know you might not think it's possible but, you have to completely not think about it. At all. Blank it right out of your mind. Put your mind somewhere else but never on the tinnitus. Easier said than done I know first hand but, it could work for you. It could take a while but hopefully this can make things better. Your ENT didn't give you an explanation because there really is no explanation. Sometimes it's associated with hearing loss but many people get it for no particular reason. I think it's more related to your recent health issues than you think. Keep your mind on other things and you have a very good chance it will just go away. Do you have an acoustic neuroma, probably not. They are somewhat rare and at your age rarer yet. There have been cases at younger ages so there is a chance but, usual symptoms would include balance issues and hearing loss. I don't see those issues in your post. Getting an MRI will be a personal decision that you and your family would have to make. Anyway I hope this wasn't too much rambling. Good luck to you.