Finn's Mom put it the exact way I was goign to say it. He was merely a biological factor in your life. You didn't mention what your stepfather is like, but I suspect he is the dad your "father" never was or could be.

You need to realize some people are poisonous to you and your life. Look at how one conversation has you calling yourself a big fat failure. You are not a big fat failure- HE IS! A failure as a father to care for his child. A failure as a husband to cheat on his young wife, and I suspect there was a lot of emotional abuse from him to control his wife. A failure as a human being to respect another human being, to respect their feelings, opinions, and choices.