Mishac dear... I felt the "better off dead" feelings so much, and really only stopped feeling that way a couple of weeks ago. My turning point was when I knew in my heart what my head already knew, and that was that my STBXAH is not my dream come true, more like a nightmare with a potentially bad ending.
Some of the things that helped me survive that several months of thinking I was better off dead were (not necessarily in this order): Trust in God when I remembered to think of Him, DV counseling, prescription antidepressants from my doc, dear friends, taking walks with my doggie, and going to work every day. Other people find exercise, shopping, hot baths, cooking, things like that to be helpful. You WILL get through this, my dear. Truly you will!