If i am going on medicare in 2 years and not sick, should i hold off seeing doctors so my medicare supplemental insurance wont cost more or exclude new preexisting?

Yes: You should have a primary care physician certainly before age 65! routine testing to prevent and find disease early include screening mammograms, bone density, colonoscopy, eye exams, bp, cholesterol, vit d levels. Thesen are a few of the tests done during a healthy adult exam. In women it also include pap smear and men a digital rectal exam of the prostate.