If you are not already using a Google Chrome browser, it may be well worth trying. It comes with a free grammar check extension called Grammarly which helps you analyse your spelling and grammar when communicating online.
This may be a great place for you to start monitoring your own sentence constructions and get immediate feedback on how you are doing with grammar. You can even have the website version scan your essay or other writing pieces for a fee here:
Let me know if you find these useful for your IELTS Writing self-practice. If you have also come across any helpful tools/websites to share with other IELTS students, do let me know or share them with us in the Reply box below.