Have nightmares everynight. Of my gf breaking up with me. Was deppresed and suicidal before she came along, dating for 1 year now....?

Understandable. You were in bad shape & got over the depression after being with her you probably fear your depression will return if she leaves. You need a work up and treatment to prevent future depression and help restoring your self confidence.
SSRI? Prazosin? See your doctor/psychiatrist. If medication is appropriate, and if the doctor diagnoses depression/anxiety, an antidepressant such as an ssri [zoloft, lexapro/celexa, prozac] or other antidepressants may help. Prazosin or Clonidine may reduce nightmares. Lithium may be helpful if suicidality is a serious concern. Doctor should also observe over time for possible bipolar.