Stefan has indeed been a vampire for 148 years, he turned in 1864 and it hasn't been his birthday yet, but tell me if i'm wrong...
No you’re not wrong. That post was just saying that the last 146 years of his vampire life were horrible. He didn’t say 148 (which is how long he’s been a vampire) because he was with Elena for 2 years. And they were the best years of his life.
Stefan stated that the last 146 years of his life has been ruled by the pain of being a vampire. Daily reminder that he’s a 165 year old vampire right now, which means that he left out the 2 years of being with Elena, because in those years he truly was the happiest he’s been in all of his vamp years.