Well as a certification doctor (and hopefully one of the 5% alluded to above) I can tell you this.
Medical records are very important to document the condition. No one, including me, can just look at you and tell you have chronic pain or nausea, your record tells me that because you sought care and were treated for it. As a doctor, I am aware that many medications have the specific side effect of nausea. Show me you are on those meds (and have records from the visits were you got them) and it goes a long way to justify the certification. I have to not only be convinced, but I have to be able to convince a judge/jury as well if you find yourself in a section 8 hearing down the road.
Records are simple, I can do that. But if you have NOTHING in the line of records, you are faced with several choices. Either generate them by going to the doctor, or there are some good clinics (Michigan Holistic right there in GR) that will work with you over several visits, pain/nausea logs, etc to properly document a previously undocumented condition. Call them and ask about it if you are interested. DO NOT go to some clinic that has you fill out a form or 'affidavit' saying you are sick and then sell you a certificate THAT visit, make sure it is over several visits. A single visit for an undocumented condition will be viewed by the court like me signing a paper I'm pregnant and getting prenatal vitamins. It just won't fly in a Section 8 hearing.
Whatever you do, the more documentation you have the better.
Good luck man.
Dr. Bob