Can’t sleep  

See your doc.  Get a sleep study.   If you have OSA, have to do one of three things and show effectiveness 1)  CPAP, 2) Use of a device i.e. mouth piece or 3) surgery.  For the CPAP, print off your sleep report and take the Airman's Disclosure Letter that you fill out stating that you use the thing to your AME.  I note from your PCM or Sleep/Pulmanogist stating that all is good after treatment is helpful.  Your AME will issue a certificate.  For the initial Special Issuance, it will go to OKC.  After that, your AME can re-issue the Special Issuance.  Go into the AME guide; it will spell everything out.  Easy.