(((brephi))), i've seen you post before but cannot recall if you are seeing a therapist. so much of what you posted i could relate to when i was early in my therapy and trying "to get a life". when we deal with depression it affects so many facets of our life. try to not be so hard on yourself. be kinder to yourself as you would a friend that came to you feeling as you do. i know you would comfort her and reassure her that she was of value and worth.
depression can cause many things...we can make poor decsions, we cannot make decisions, we are overwhelmed with everything, we don't understand why we can't "get it", etc.
i hope you are seeing someone who can help you untangle all that's going on with you. it's a huge task to try to do it alone. i don't think i could have gotten better with my depression if i had not had help.
do try to realize it's not your being worthless...you are of value and a unique human being. there are many things of worth about you. the depression clouds our perception of who we are. please let us know how you are doing. you matter to us and we care about you!