Wow ... it feels as though I could have written that exact same post myself.
(((((((((((((Christina))))))))))) I'm so sorry for the pain you're experiencing right now.
Can i just say that I also quit smoking a month ago (stress, anxiety, etc), and that when i get in fights with my roommate (only really close friend here) it can get me so down. University stress can be so hard (i'm also in Uni), esp on top of everything else going on. I'm also sorry about things with your mom .. i can only imagine that adding so much stress and pain.
What to do about SI.... well first off, hold on to the fact that you were able to stop before. That in itself is a HUGE accomplishment. Try and keep yourself busy - whether that be with school work, friends, exercise, art, music, reading, whatever it is you like to do. I'm a pretty big hypocrite saying all that .. but like many others here, i'm doing my best. Focusing on my breathing helps a lot too. I find when the urge to SI is the strongest my breathing speeds up and i experience anxiety... breathing is definitely one strategy that can "bring me back" so to speak.
Keep posting on here too though ... there are lots of great people who want to help, and are here for support.
Take care of yourself
Jacq