I'm sorry your feeling so down on yourself.
When I read your post the one thing that jumped out at me is the positive things they said you turned into a negative. I know its hard to "see" anything positive right now your too close to actually see any ..
Kinda of the " your too close to the forest to see the trees" kinda thing. Sounds like your self esteem is a bit low and that is normal I think damn near everyone has gone through it at some point in there lives.
I'm sure seeing a Therapist would be beneficial. Keep posting here it's good to have a place to unload our problems.
Good luck on your new job