Have you talked with your advisor recently?  We don't mean e-mail, but a real face-to-face, voice-to-voice conversation.  If not, please stop whatever you are doing and CALL YOUR ADVISOR.  Make it a discipline to check in at least once every month.  Tell your advisor where you have made progress, where you are stuck, and where you have questions.  If you are not comfortable in asking for help, then ASK US TO HELP YOU ASK FOR HELP.  Your advisor wants you to finish the dissertation, and so do your friends, colleagues, and family.