@TakingItToHeart,
These people are all correct, sweety. (Well, not sure about adding a pet to the equation...) The problem is that you didn't get the proper adult help in learning how to esteem yourself. When you value yourself in a healthy way, other people may be mean to you - it hurts -
but it doesn't affect how you feel about yourself.
As long as your dad belittles you and makes you doubt yourself - the bad parenting is exacerbating your poor esteem foundation. You need some relief from this.
I think we have some people here who may be able to give you some good ideas about how to turn this bad pattern around.
I know the right thing to do is to strongly suggest you try to find a therapist to help you learn how to respect and like yourself. If you can do that, do! If not, I have some ideas if you want to hear them.
and btw, you are a wonderful, beautiful human being. Seeking help is a sign of strength. This journey you're beginning can lead to a satisfying, happy life. You will be ok...and better than ok in time.
Your dad may be right that you lack social skills. Big whoop. (He's lacking a couple of parenting skills...) Anyway, you can develop them. If he says things like "you're not going anywhere in life" again, I hope you tell him (calmly, but sincerely) that having your parents put you down instead of give you concrete tools to improve certainly isn't helping. Maybe if he starts this mess again with you, you can say - "well, if you're unsatisfied with my social skills, why don't you take me to a therapist and let's all discuss what's going on." I hope he knows random negative criticism only makes it worse.