I think you may be very close to the center of the target on this one. Of course, there is no way to know for sure, but I have worked with many people, both younger and older, whose discovery of a parent’s affairs has led to their becoming extremely sensitive to issues of trust and honesty. Although it was your mother who was most directly betrayed, in a pretty direct way you were betrayed as well.
The break-up of the marriage was not in any way related to you, yet you have had to bear the brunt of what happened between your mother and your father and this other woman. The family unit broke apart, your mother was emotionally devastated, and you were left with the remains of the destruction–a broken family and the betrayal of your trust in the security of your family unit.
I don’t know if you have ever dealt directly with the emotional and psychological issues around your father’s deceit and the break-up of your family, but these are issues that tend to fester inside of us if we never look them in the face and work them out in our own selves. I would strongly recommend seeing a therapist and doing whatever work is necessary, psychologically and emotionally, to really come to terms with your anger, sadness and the betrayal that you, too, experienced as a result of your father lying.
It is very likely that your extreme suspicious reactions to people are related to this major event in your family’s past. Please understand that I am not suggesting that you should become tolerant of people who lie or not react at all to being at the effect of another person’s dishonesty. You have the right to be concerned, to inquire and to be angry or end a relationship with someone that has lied to you.
However, carrying around the degree of reactivity you describe can really hinder your relationships with others and may sometimes cause you to throw good people out of your life due to misunderstandings and misinterpretations of people and situations. By doing the necessary work to reduce your tendency to overreact, you will be better able to distinguish who is worth trusting (even if they make an error in relating to you) vs. who you really need to purge from your life. This work is emotionally difficult, but well worth the time and effort.