Your story is very similar to mine. I had a pretty rough childhood - alcoholic parents, emotional and some physical abuse, very overweight, had a hard time at school, never participated in sports and activities and spent a lot of time alone since I was very shy.
I did the victim mentality thing as well - and I'm still struggling with it from time to time. But your past doesn't have to dictate your future. Today, I'm doing great. I have a lot of very good friends, I'm more outgoing and less afraid to meet new people and have a great job.
As for feeling good about yourself and achieving a higher self-esteem, I suggest looking into
unconditional self-acceptance instead. Self-esteem is basically just your own very subjective opinion of your worth as a human being at this time - and can vary greatly. Connecting it with not making mistakes, excelling at your job or sports, having a loving partner or whatever sets you up for inevitable failure as does comparing yourself to other people.
Self-acceptance trancends these things and allows you to accept who you are, regardless or faults and circumstances. Besides, high self-esteem can actually lead to serious problems as well - that are more likely to affect other people negatively.
You can always do something to lead a life more in line with your values. Find out what really means something to you and set goals in line with those values. For instance, if you value being fun and social, then set very concrete goals which support that value.. like "I will attend this party on Friday" or "I will make smalltalk with two strangers today".
When self-defeating thoughts or feelings pop up - like being scared of following your dreams - just accept them and let them be. They are just thoughts and feelings.. nothing more than that. Not facts. Not something you have to act on or get rid of.