That is hard ~ so thoughtless of someone who is supposed to cherish, protect and fill you with a positive self-image to steal that sense of value from you. I am so sorry your father did not see that you are a valuable, unique individual - there is and never will be anyone like you. You are rare, precious and a treasure. I'm so sorry someone could be so callous and hurt you like that.
I know how hard it is to believe we have value ~ from a young age I was given the sense that I, too, was of no value to those who should have protected and been loving to me. I have only just begun to work on believing that anyone who might tell me I was important, cherished in any way, wasn't trying to use, abuse, and discard me. It is helpful, when you are able, to release the anger (or rage) you have for your father doing that to you. Maybe write a letter to him (even though he's been gone for 20 years) and let it all out, how angry you are, how you feel about yourself, how you feel about him. Allow yourself to purge it all from your mind and your heart and once you've done that you may be able to begin to think about how valuable you really are. Make a list of positive things about you. (when i did this i started with silly things like i love ice cream, i'm not hated by everyone that meets me and graduated to I'm a good friend to others...). Try to get that voice and those words out of your mind. Replace it with positive thoughts to build you up and make you feel good. You deserve it. You are worth it. Don't let anyone steal your value - you are a precious gem!
♥