Dealing with Abandonment Trauma in Relationships

I've had some pretty extreme relationships, especially given abuse from my dad in childhood. As a result, I have an excessive fear of abandonment, even from bad people in my life, and I panic and have immense depressive episodes when I feel they may be slipping away. This was particularly true in my two relationships. I was suicidal at each thought of or event of almost losing them, so when they finally left because my childhood and past trauma (physical, sexual, emotional, mental) became "too much", my suicidal bouts over them were uncontrollably destroying me. it's been 6 years from my first relationship and 2 years from the second one. I've only been in 2, but this is my third and I really don't want to repeat this in my current one.