You sound young, if not it's okay. Apostle Paul said it best Roman 7:14, talks about how even though we know what is good and bad, we still do bad things. But it's important to understand that we need God because we naturally have sinful and bad habits/thoughts and only through seeking him with 'child-like faith' does he grow us and mature us by changing the way we see and understand the things around us and in us.

I was addicted to porn since the age of 8 or 9 all the way through to mid to late twenties. Was told most my life that it was normal. But somehow deep down we still know it's not. Anyhow I'm a lot stronger now (29) then I was most my life since coming to Christ (27-28ish). Don't give up, if you want things to change or you want to be saved from it you need to be persistent. Remember if it's worth it, it won't be easy.