It's not wrong to want to feel good about yourself. It is dangerous not to nourish your body and keep it healthy, or to keep up the damaging cycle of purging. Sweetie, it's difficult but you need to take care of your body and yourself.
As for being ill, it's good to take care of yourself, too. If that means taking a proper dosage of medication to help you sleep (not a harmful amount), and staying home from uni to rest and gather some strength, then you should do that.
Please be safe.
We are here for you if you want to talk to any of us privately. We all care about you and hope that you are feeling better very soon.
*hugs*