Two issues pervade your question: the fear that you will end up just like your mother and the feeling of pain and torment that you ended the three week relationship and wonder if you did the right thing.
First of all, I am going to say something that will blow your mind. The reason why you fear that you will end up like your mother is because your unconscious mind wants you to end up just like her. Now, that you have picked yourself up off the floor and stopped screaming at me for being so stupid, can we talk about this?
Trust me, in the language of the unconscious a fear is actually a wish. I know it sounds crazy but that's the unconscious for you. Even though this makes no sense to you, and you don't believe me, can you, for the moment, examine why your unconscious might want you to end up like your mother.
I can think of two reasons. One, because if you end up like your mother, with either abusive or spineless types, you will have a chance to relive the pain of your childhood. No, your mind isn't out to torture you, it actually craves to recreate the past so that you can hopefully heal the wounds.
So, there is a method to this madness. Recreate and heal. The reason why you feel so rotten to have given up this loser that you were dating is because your unconscious mind is grieving the lost opportunity to heal.
Remember, we humans are not of one mind. Your unconscious mind has one plan--to recreate the past and heal-- and your conscious mind has another--to protect you from bad relationships.
So, how can you reconcile these two parts of yourself? Obviously choosing abusers and losers and recreating your childhood will not produce a good result. As I have explained previously, most of us are driven by a repetition compulsion, the unconscious push to recreate the traumas of childhood and then work for a happy (search my Advice Archives on this subject). I have also explained that our happy endings rarely come through such repetitions because the partners we chose to dance with are as damaged as the people that let us down the first time. Hence, we find ourselves stuck, chasing our own tails, trying to get blood from a stone or attempting to make the leopard change its spots.
So, if recreating the bad relationships that your mother had won't heal you. Then, what will?
What I think you need to do is: 1) recognize your wish to recreate the past by choosing losers and/or abusers; 2) remind yourself that you will never find healing by choosing carbon copies of the losers you were raised with; 3) identify the type of father you dreamed of having; and 3) actively seek that kind of man.
My best wishes to you. You sound like a very bright and lovable woman who deserves to have her dreams come true.