more alone than ever

i have always hated being alone. maybe its an abandonment issue, maybe its my ever-present insecurities. when i am in a relationship and my SO wants to do something i haven't been invited to or cant do for some other reason, it throws me into a depressive fit and i have all manner of thoughts of self-harm and suicide. i cant shake the feeling that people are just trying to get away from me, that they've grown tired of me.
recently i had an abortion. while i was pregnant, my SO was incredibly supportive and understanding of the nausea and the mood swings and in addition the emotional turmoil that comes about from falling madly in love with something and realizing that it is not time for it to come to be. two days after the procedure, he went home to his family for 6 days. it was by far the worst 6 days of my life. he rarely called or messaged me, and when i attempted to contact him most days i would be left with no answer for 8, 9, 10 hours at a time. i told him how i felt about this, how hurt i was that he wasn't making an effort to be there for me, and his response was riddled with excuses about how he had been on a boat, had not had his phone with him,

Hello & Welcome, Scientificpenguin. (Feel free to ignore these questions.)
How long have you suffered from depression?
Do you experience "depressive fits" in situations not involving your SO?

Please make yourself at home.

i've had problems with depression for many years, id say at least 10. i feel ashamed to say it but generally my bad periods are associated with a relationship that's having problems or ended. i'm what my mother likes to call a serial monogamist, ive been in steady relationships for all of my teenaged/adult life. i absolutely have more severe problems relating to my SO than otherwise, but the last few weeks ive been having a very difficult time dealing with the abortion as well, and i dont feel that i'm getting the support i need/deserve which i think has added a lot to the issue.