For many months straight lines look wavy with my left eye. Have myopia and astigmatism. Causes? Which should I see a optometrist or ophthalmologist?

Exam needed. I would suggest you see an ophthalmologist for dilated eye exam to confirm the retina (back portion of the eye) is normal. Symptoms you discuss suggest to rule out retina changes. If retina is normal, then you may need an update on glasses possibly your astigmatism has change.
Fluid in Retina. In your age and being in one eye only most common cause of this is collection of fluid in the retina called csr. Amd may also be a cause. Although is may be a variety of other diagnosis. You should see an ophthalmologist and have oct of your retina and optic nerve done.