What kind of score are you required to get for your IELTS? I recently sat it, and as English always was my worst subject at school, failed at the first hurdle! I scored a 7 in my writing and 8's and 9's in everything else! I needed all 8's!!!
I'm a chef at a public school, and enlisted the help of one of the teachers there, who gave me 3 two hour lessons on my writing, and law and behold I passed 2nd time. scoring 8, 8, 9, 9.
A lot of what he told me was think about what you are writing, and don't use the same word over and over use synonyms and antonyms and display a wide variety or vocabulary and you should be fine.
Don't Worry!