Sorry about your struggles. I agree with others about seeing a therapist and psychiatrist. A combo of meds plus therapy plus self help can really get a person to a better place. I do believe as a person who often is "debbie downer" that negative self talk makes you even feel worse. So what I have been working on is even if I feel horrible about myself I try to say positive things or if I say something negative then I try to balance it out with a positive. In time I am hoping it will make me feel it with in.
You stated you will be coping then fall apart and I wondering if you are letting things build up and then you so to speak explode? For myself I try to take things as they come rather then put something off or if something upsets me I try to speak up so that it does not build within. Also if I feel I need support I reach out in ways I can.
Everyone is different but I hope you find what works for you to feel better