To the OP, you will find with more experience in meeting people and the more relationships that you have that there are certain character traits and signs that become very obvious and easy to detect in potential mates. It gets easier with experience but ultimately you have to develop a skill set in order to find the people/person who will treat you with respect/honesty.
I can help you out in this as this happened to me last year. My advise is some meaningless casual sex, no really. I still don't trust women, it'll take time, but for now just have some meaningless sex, seriously it helps.
I think some people may have read the op and then projected something on to you from their own experiences. I don't see any reason for anyone to blame or attack you here, other than because of their own issues. So as been said, therapy is one way to go. I think that, perhaps with the help of a therapist, going back and figuring out what happened to your relationship might help alot. Knowing what went wrong might help you avoid problems in the future. I don't know if the relationship with your ex has been so destroyed that you can't even talk anymore. If you could talk, it might help. Maybe she did what she did because she was angry at you but didn't know how to communicate it. Maybe communication in general was a problem in the relationship. Maybe she was just selfish and irresponsible. Maybe she decided to sabotage the relationship because she is self-destructive, has low self-esteem, was scared of committment, etc. She may have had a negative relationship in the past and (not unlike some posters on this thread) felt the need to project her hostility on to you. If it's possible to talk to her, you might be able to let go of some of the emotions, even if you get no further than an argument with her. If she could get to the point where she could apologize to you, I think that would go a long way. Her going to therapy also (or the two of you going together) could be mutually beneficial. If she really went through agony with the loss of the child, if you could see that she did what she did becuase of her own issues, or if you also found something in the relationship that you did wrong too, you might be able to forgive her. And that would be a huge step toward moving on. I don't think you should try to force yourself to forgive her if that's not what you feel, but if forgiveness comes about naturally, It could be a real blessing. If you have stuff from your old relationships that you don't work out, it has a habit of sabotaging your next relationship. Maybe she is really such a bad person that you would want nothing to do with her and trying to talk would be useless. If she is not truly evil though, working it out could be a big part of the answer.
No one destroys your ability to trust. YOU choose to react. Step 1: Hold yourself and only yourself responsible for your feelings and reactions. Beyond that, it's child's play.