compulsive lying

Hello, I am an adult female (23) living with my parents for a year while i save money for grad school. Over the last two years though, i've been compulsively lying to my parents about almost everything (like the fact that i didn't graduate college when i said, I got into debt) and I need to stop. I don't want to hurt them but I think i'm afraid of their reaction to news even if its something thats not in my control. My mother can be pretty volatile in her temper, but i'm ruining my relationship with them because of the lying and I need to stop. What should i do?

Tell the truth. At least that way you know you're not feeding the anger. If you think she is volatile now just wait until she finds out you're lying to her. When you lie to avoid confrontation you are depriving the other person of all the facts in the situation to which they may have to make a decision on.
You are also telling them that your judgment is much better then theirs to decide which facts you will provide them and which you won't.
Hope this helps.