If you have any of the books that contain practice IELTS tests (e.g. the official Cambridge books), why not use the listening test answers to check your spelling? Here's what you could do:
- Ask a friend or family member to read the listening test answers (at the back of the book). Write each answer down, then check whether you made any spelling mistakes.
- Or, record yourself reading the answers aloud, then listen to the recording and try to spell each word correctly. To make this more difficult, test yourself with the recording a week later.
Imagine if you worked through all 11 Cambridge IELTS books in this way. I think you would feel much more confident about your spelling.