How can I improve my nearsightedness? Is there a natural way that doesn't involve lasik?

Unfortunately not. Your prescription is determined by the physical size and shape of your eye. Because of this, there is no way to change your prescription other than with refractive surgery.
No. Besides wearing glasses or contact lenses, there is no natural way of improving nearsightedness.
Myopia. Options for myopia correction include glasses, contact lenses, laser eye surgery (lasik, prk, lasek), intracorneal ring segments, clear lens extraction, phakic intraocular lens implant, orthokeratology, or other treatments. There is no natural way to correct the myopia.