Should I do a paternity test?

I have been married for seven years and have three children a boy and two girls aged seven, five and three respectively. We were living as a happy family until recently when one of those 'know-it-all'woman in our estate shared with me some disturbing news.

During a casual discussion she kept talking about how cunning and unfaithful women have become and how many men are raising children fathered by other men. When we were parting, she hinted that I should confirm the paternity of my son and the younger daughter. This bothered me for some time until I got a chance when my daughter fell ill and I asked for a DNA test. The results confirmed that I was not the biological father. This has put me under intense stress to the point that I fear doing the test for my son who I love very much. I think there is some possibility that he is also not my child. I feel betrayed and confused. Should I go ahead and take a paternity test for the remaining children? {TNK}