Your husband 's infidelity traumatized you. One feature of a trauma syndrome is a terrible and lingering fear that the trauma will occur again, in this case that you will be cheated on again. What you need to figure out is whether your fear is founded in reality, that is that your unconscious has chosen another cheating type; or whether your fear is simply the result of the previous trauma.
To sort this out, you really would be wise to do a complete self-analysis. Study whether you have a history of abandonment that dates back to childhood. Did one or both of your parents abandon you emotionally or physically? If your answer is yes, then we have to suspect that your unconscious mind chose to marry a man who was an abandoner. We all choose life partners who recreate the wounds of childhood. Humans do this partly because they are creatures of habit and like to stay with familiar experiences (familiar pain is more comfortable than the discomfort of the unknown); we also recreate childhood traumas in order to heal them (see my Advice Archives under repetition compulsion and unfinished business).
If you, in fact, chose an abandoner as a husband because you were trying to fix an early wound, then you do have good reason to be concerned. Your concern, in this case, is a signal coming straight from your unconscious mind which is alterting you to the fact that you chosen another abandoner and that it's only a matter of time before history repeats itself. If you can find no pattern of abandonment dating back to your childhood, then I would feel safe is assuming that you are simply dealing with the aftermath of a trauma that you suffered in adulthood.
To help yourself heal from an adult trauma, you need to remind yourself that lightning never strikes twice in the same location. That is, just because you were struck once doesn't mean you will ever be struck again. Your past doesn't equal your future. If you still find it hard to let go, then seeing a hypnotherapist would be your next stop. This type of therapy can help you to reprogram your mind so that it stops expecting a repeat disaster. Let me know how you make out.