Though I played the viola years ago, I still have an appreciation for music (I'm still biased toward string instruments, the violin family in particular) and musicians. I truly hope you can find that choice that'll make you feel most whole and best, giving you that worthwhile feeling that you long for.
camoshark
Your little story is fairly similar to mine, actually. I began taking piano courses at a young age, and became fairly good at it. I had a good teacher, which was a retired professor from the conservatory, and essentially taught me most of the musical knowledge I had until I reached college, which is saying a lot.
Unfortunately, once I reached secondary school, piano was not offered in band class, so I had to change to another instrument. I had to pick between sax, trumpet and percussion. I tried the sax, but I had a hard time producing a sound, and plus I didn't want to play what everybody else wanted to play. I then had to pick between percs and trumpet, but I tried the trumpet first, and just fell in love with the instrument and chose that one before even trying percs. I don't know if I would have taken percs if I had given it a shot, but the idea of one day being able to play what my uncle (world-reknown player) could do had me hooked.
I thought that would be all, but once I hit a certain age, my father decided it was time that he taught me a bit of his art, or congas and djémbé. I didn't think that would de much at first, but once I discovered the world of percussion, I was once again hooked, and almost 10 years later, I couldn't be more thankful! To this day, I'm discovering new instrument I want to learn on a daily basis, and my formal training in almost all types of instruments has helped me tremendously.
So the moral of the story is: Don't be shy to try new things, you might just discover a passion you didn't know you had!