Hi crawler, SORRY no professional help here either but just some thoughts.
I'd say that we're all going to be influenced by outside opinions/trends at times but that all goes towards helping us (sometimes gradually) discovering what we like and what we don't like. Experiencing and trying new and different things all adds to finding what gives us satisfaction. And that can/does change through life.
If you liked particular music or trends at times don't let that take away from the fact that you liked/enjoyed/felt fulfilled by them wherever that came from. At that time it WAS you. It was what mattered to you. And sure, you've changed you "allegiance" (?) at times but I'd say everyone does that through their lives with some things it's all about us moving on and finding different things that spark a passion in us. How you felt is just as important and it adds to who you/we are.
Maybe you'll change "allegiances" less when you get older and get stuck on more things but life should be about staying open minded to a point and you're doing that by allowing different concepts into your life as time goes on and seeing things differently while still holding onto the identity you're really feeling at the time and keeping the passions you have at the time alive.
As for the religion bit, aiming for their happiness, do you think that it might be as much about finding your own happiness (that may be through religion that may not) and keeping a hold on that without challenging the "why's" and "wherefore's". You have had things in your life that have mattered, maybe give them the importance and your happiness the value they deserved?? and allow more things (however seemingly insignificant at the time) into your life to allow for your PERSONAL meaning of happiness.
Don't be afraid to stand out and be yourself, maybe add variety (IF you think you need to) alongside things you like/believe in. DON'T dismiss what you're liking/believing but maybe keep on using/considering different influences too.
But I wouldn't worry too much from what you've said, we all can change through life experiences and that can be a good thing with new experiences along the way if you can really value or use those experiences.
As for your dad it may have left you some issues you need to look further at but it doesn't HAVE to have left issues if you feel it's something you have kind of moved on/away from. Some people can naturally adjust to circumstances and find other things in their life which can compensate, moving on well balanced. Maybe there is some/any of that in you? And maybe the "I don't really care" bit has a lot less importance than perhaps you're digging for???
Anyway, just a few thoughts, best wishes.
Alison