To get from your situation to becoming a PE teacher, I would take the following steps:
1. Sit maths (and maybe science) GCSE,
2. Take an Access to HE (Science) course, preferably one that includes a physics module as well as biology (physics will be useful for step 3),
3. Do a degree in Sports Science or Sports Coaching (look for one that supports you to get professional coaching qualifications alongside your degree),
4. Take a PGCE to get qualified as a teacher.
That should take you 6 years altogether, but the journey itself should be enjoyable if it's the right career for you.