You’re not doing anything wrong.  You have valid reasons to feel the way you feel.  First, be grateful that you are still young and have time to work on addressing the issues that are affecting you.  Look into finding a therapist to work with.  If you have financial constraints, look for low cost therapy or free group therapy.  Try to reach out to whatever support system you have in the form of family, friends or co-workers to develop a network of support and help with childcare .  Try to take care of your body as best as possible with good nutrition and exercise.  Avoid people who don’t serve your best interests.  Read some self help books, pray, try meditation and deep breathing.  Being a single parent is challenging but it is better than being with a partner who isn’t good for you or your child.  I think trying to find a therapist is probably the most important step for you.  Take baby steps in implementing changes in healthy self care and just keep trying to do things that lead to positive changes for you and eventually things will get better for you.