I had the same experience with Bactrim. In December too, no less. I was taking 800 mg twice a day for 10 days. This was for an infection in my leg. On the evening of Day 9, I woke up in the middle of the night and I couldn't get back to sleep. The medicine had given me bad insomnia all week long so I was not too surprised about that, until I went to another room and I realized that my ears were ringing! Needless to say, I didn't bother with Day 10 of the pills.
Long story short, I had a similar experience with the ENT, who basically said I would probably have to "wait it out." I have normal hearing and healthy ears, apparently. I also lost about 20 pounds in December after the onset of this. My tinnitus is also high pitched. It was pretty bad on the first day but came down a little bit, and was fairly stable for about a month. Then, the ringing seemed to disappear (almost) for about a week in January. During this time I was ready to declare the whole episode to be over. However, it returned. Then I got a bad cold in February which turned into bronchitis, which exacerbated it a little, or at least it changed the sound. I've gotten over the bronchitis, but apparently the tinnitus hasn't yet gotten the news.
I'll write out my whole story sometime. Meanwhile, I am convinced that the Bactrim played a key role in starting this. What the mechanism is, and whether there's any way to reverse it, or the probability it may correct itself over time, I don't know.