The question is: do you really think liking these things is a problem or do you just want to stop liking them for appearances?
Hey, we allll like stuff that others think is strange. I like it when characters go through a lot of pain, my friend likes sewing her hand. Now, sewing your hand is not a healthy thing to like, but enjoying a CHARACTER's pain is okay. You need to look at this problems and label them. Write them down on a piece of paper and put them into two different columns: FINE and UNHEALTHY. Examples of things to put in the unhealthy column: hurting yourself and others, mocking people, things that are physically unhealthy (eating raw or moldy food), putting off assignments. I know this sounds funny, but it might really help you sort yourself out.
All the stuff that goes into the fine column is worth keeping. Watching lesbian porn, thinking jellyfish are really cute, tapping your fingers, spending time with your cousin instead of your friends. These things aren't necessarily healthy, but they're not unhealthy, so they're just fine. Once again, hard to take seriously but stay with me. I'm going to get to the point. If you want to stop liking any of the things that go under the fine column, then think again. Do you want to stop liking these things to fit in? Do you want to stop liking these things because you're ashamed?
If you're trying to fit in then stop. You don't have to change what you like to fit in. You may have something in common with one person but still disagree on certain things. Always keep in mind that no matter how cool and collected people seem, they allll have strange things that they like and dislike. My cousin has a phobia of cereal, but she doesn't have a sign on her head saying so. Like what you like, you'll be surprised by how many people actually like that thing too.
If you're ashamed then the journey is personal. I'm sounding like a broken record now, but you just need to remember that you are not alone. Other people think they're alone in liking the sound of rubber bands snapping, but there are others out there. Everyone is ashamed of something, you're not some damned thing cursed by the strike of lightning. You deserve kindness. Be good to yourself. Be gracious to yourself. Shake off the shame and start really enjoying what you like. You are not alone.
Of course, anything in the unhealthy column needs to go. You like stabbing your thigh with needles? Sorry, it's gotta go. You like eating raw beef? No way. You can try getting a therapist for these things if they are becoming or already are obsessive. Otherwise, talk to a friend that you trust or a school counselor. Cry out for help, read a book on obsessive behavior. Don't let unhealthy likings become accepted. It's good if you've realized that you need to get rid of them, now move on to the next step.
I hope this made sense and didn't seem like a ramble.
Best of luck!