I did a CELTA last year. I wouldn't worry too much about struggling with the course, you don't need any formal english qualification (as far as I know). Chances are you already know everything you'll have to teach just from speaking the language for however long you've been alive, it's just a case of learning how to explain that to others. During the course you study the specific bits of grammar or whatever it is you're going to teach next lesson, then repeat until eventually you don't have to refresh your own memory so much.
I did a CELTA last year. I wouldn't worry too much about struggling with the course, you don't need any formal english qualification (as far as I know). Chances are you already know everything you'll have to teach just from speaking the language for however long you've been alive, it's just a case of learning how to explain that to others. During the course you study the specific bits of grammar or whatever it is you're going to teach next lesson, then repeat until eventually you don't have to refresh your own memory so much.
Feel free to PM me with any questions!