jessers,
Welcome to SR! I'm sorry for what has brought you here but know that you will find alot of support for the very experienced people here. I would encourage you to read the stickies at the top of the Friends and Families of Substance Abuse page and look into NarAnon or AlAnon meetings in your area.
I am not in a relationship with an addict, it was my adult son that brought me to SR, so I do not have the same sort of experience.
I just wanted to respond because "no one understands" really struck me as a "unique" sort of vibe. In my opinion, your situation is not unique because there are so many people posting here on SR that are or have dealt with being in a relationship w/an addict. Addicts tend to be very self involved - you need to focus on and take care of yourself. You have enough on your plate w/multiple jobs and nursing school - you do not need to be taking care of this man. My daughter graduated from nursing school 2 years ago and I know how hard school was for her.
Good luck and others will be along shortly to give you experience, strength and hope for you.