up and down

I seem to be hitting highs and lows a lot more than I have in the past.  Before I would have a good 6 month to a year stretch of depression, then I would be fine or fairly happy for a while, but for the last month (since I stopped SI?) one day I'm excited and ready to change my life, the next day I'm down and ready to end it.  Now, don't get me wrong, I'm not the type to kill myself on a whim, or put an attempt at it.  I don't plan to 'attempt' suicide, when I'm ready to go, it will happen.  And that will be that.  Of course, death takes a lot of considerations, there are a lot of variables to be determined.  How do you know when you're really ready to go?
 
Well, I don't know that I'm at the point of suicide, but when it comes to those thoughts, the only thing that has distracted me from it was SI, and without it I'll be alone with myself. :(
Goals: start working out and jogging, start my meal plan back up, go back to IIT, get into a research project or start my own research under a professor's supervision.
Goals: waste away alone in my room, starve myself and binge so I screw up my body even more, start hitting my ribs (my favorite place to leave bruises), eventually realize I'm really going no where and I'll never be good enough for anything, die.
Which path to choose.. I know what I'm supposed to do, but is that what I want to do?  If I'm supposed to follow my heart, what if my heart tells me I have nothing to live for?  Things are much too complicated, I'm just gunna stay on autopilot a little longer till I can decide..