I never owned a car, I bike everywhere I go, and I don't eat meat when vegetarian options are there. I buy used when possible.
I still own a computer that uses a lot of electricity for executing games and movies, I still order new stuff online dependent on transportation, and I have to use a plane to see my family and for work that requires me to use it (otherwise I get fired).
I am still part of the problem but it's really impossible to be part of contemporary western capitalist society without damaging the world. The alternative is to move into a forest and become self-reliant.
No you're not. "What have you done" is always a faux argument. Believing climate change is real doesn't mean we have to live like a hermit. You've already done more than your fair share and the biggest changes cannot be done by individuals, they are industrial regulations and policies that can only be enforced by the world governments.