I skimmed your post and caught some of it but will have to reread when I am less tired.

It sounds as though you have two problems: relationships and a possible mental illness. You mentioned that you have recently been diagnosed with depression. When you said you started staying up later and later at college I wondered if you might possibly be bipolar. Not sleeping much while at college was one of my first signs of bipolar. Perhaps you could take one of the bipolar tests on Psychcentral.

What antidepressant are you taking? Are you taking it consistently? How is your sleep now?

Have you considered seeing a therapist?