I'm not a doctor, but I have never heard good things about Wellbutrin. Your comment that your doctor let you diagnose yourself is concerning. It doesn't sound like you are getting proper treatment.
You are NOT a loser!!!! I know I don't know you, but I feel sad that you see yourself that way over something that you have not really received help with; despite having asked for it.
A few suggestions. 1. DO find a new medical professional, and check out their references before seeing them. A general reference can even be found online for free. A more thorough one for a slight fee. I'm sorry, I cannot think of the website for it, but I know several pop up when I do a search for physicians (watch for the ads that pop up).
2. Get out every day, and/or do something nice for yourself. A short walk can do wonders!!! If you have a park nearby go there and just try to take a mental break.
3. Take things a day at a time, (or even an hour or minute at a time). You have moved into a new role with tremendous responsibility, and it can be a lonely, unsure place.
4. You may have a hormonal imbalance (from the pregnancy). Have you tried your gynecologist? (If your gynecologist is the one that prescribed the anti-depressants, that it's definately time to find a qualified practitioner to properly diagnose and treat you.)
Whatever you do, I hope you know not to go off the Wellbutrin all at once and/or without doctor's supervision.
Where is the father (and/or your family) in all of this? I hope you are able to ask them to help you get needed help. When you are feeling that low sometimes our loved ones need to give us a hand up. I hope you will ask if you haven't,and I hope they help.
Take good care of yourself. You are worth it.