I agree with Yumeji telling them how you feel is a good thing, but if that doesn't work out then find new friends. If your trying to be like them and follow their interests- don't, stop now and just be acquaintances, and you find friends that like the same things you do and listen and play with you as much a you do them. I've been a third wheel in, honestly I got nothing from being friends with them. So one day I had enough and stopping clinging to them and started being myself- then I started meeting new people and hanging out with people I usually don't, I ended up with the best of friends. It's hard, but worth it!!!!
I'll do my best to sing my heart out, because I can't stand regretting that one word I left unsung.