Whenever I change my opinion, people always question it, like is it based off someone else's.
I tell them I legit did without any one else's support, but no one believes me.
This happens all the time IRL.
I don't mean this in a condescending way, but at your age, you shouldn't worry so much about what people think of your opinions, and especially not pay any mind to them not approving of how you reached your conclusions.
Adolescence is the prime time for a person to figure out who they are and what they make of the world around them. It's normal for your thoughts on things to flip-flop, regardless of whether it's video game stuff, political stuff, or your sexuality, or anything else. You're at a point in your life where you likely have more freedom to experiment with your beliefs than you will ever have. Once you hit adulthood, you're gonna often find yourself in situations where you will be forced to embrace certain ideals and opinions even if you don't like them. You won't be able to make as many mistakes.
It's also worth recognising the irony in people telling you that you're wrong for reaching conclusions based on listening to others. The people telling you that's wrong are, even if not intentionally, influencing you. Young people like yourself are malleable. And their words are what's making you feel this way, it sounds like. Listening to others is perfectly fine, but you don't have to listen to people who are bringing you down like that.
On a fundamental level, people should encourage you to listen to others to help form your opinions. The fact you do so makes it evident that you are an open-minded individual. That is something you should be proud of.