So I live in Uk and i am the same age as you but 2 months older so we are allowed to start applying in 2017 October for 2018 October entry in universities.
Considering how difficult it is to get into medical school I would highly recommend you take a gap year, as in do a proper yearly based internship or work experience in a qualified hospital in Saudi Arabia for a year. This will not only benefit your application hugely it will give you an insight into whether you really want to choose medicine for your career. And then apply in October 2017 for the October 2018 entry because if you really want to go to Oxford they are not going to shortlist your application no matter how good it is if you are not 18.
https://www.ox.ac.uk/admissions/undergraduate/courses-listing/medicine?wssl=1Here's what is said under the application requirements of Oxford medicine degree
"Students must be 18 years of age at the time they start this degree course. The clinical contact in our programme starts in the first term and means that younger students would not be able to take part in required elements of the course. Your application will not be shortlisted unless you will be at least 18 years old on the start of your first term (8 October 2017 or 7 October 2018)"
If you want to apply to Cambridge perhaps they have the same thing to say the only difference is that they give a flexibility if you turn 18 by the second term you can apply for 2017 entry but in your case you wouldn't be 18 by the second term
http://www.undergraduate.study.cam.ac.uk/courses/medicine"Students under the age of 18 cannot undertake any clinical elements of the Medicine course, which start in the second term of first year at the latest. Therefore, students must have reached the age of 18 by the start of the second term of Year 1 to be eligible to apply for Medicine."
If you want to apply to neither of those try going to other university course websites and look for information that shows when you can apply. If you find a course that allows application during the age of 17 then it's up to you whether you want to apply this year or next year (although i do believe it will be most beneficial to do it next year you will have more options & bigger chance of getting in)