I can understand the distress you are through. Feeling low, irritability, negative thoughts, suicidal ideas, feeling lonely, can all be symptoms of depression. Stress is an important causative factor in it. In your case the relationship discord happens to be a major stressor. There is a solution this. I suggest you both must consult a marriage counsellor for your relationship problem. Regarding the clinical depression that you happen to be through, I would suggest you to consult with a psychiatrist. With medications and suitable instructions it can be cured.
Next Steps
Consult with a marriage counsellor and a psychiatrist.
Health Tips
Don't worry. You ll be all fine soon.