The test that is right for you depends on your particular skill set.
The IELTS test tends to be more difficult for writing, whereas PTE tends to be more difficult for speaking. The OET is most suitable for you if you are a medical professional, as you may already be familiar with the required vocabulary.
The below video explains this in detail.
You may also find these blog articles helpful: https://blog.e2language.com/category/choosing-a-test/
Please email us at firstname.lastname@example.org if you would like to have your previous scores assessed by our student support team. We would be happy to advise you further.