Is this really my child?

My wife and I have been together for 24 years. We married at a very young age and have 5 children, our first born graduated in 2015.

We've been involved in a number of fights mainly to do with her desire of being a house wife and doing totally nothing to contribute to the family finances.

She's very educated and bright. She has qualifies for a number of scholarships and even did a Phd but that's all she does. Study and sit home. Being a housewife is her ultimate goal.

Being solely responsible for the family finances, I chose to go for a vasectomy since she was reluctant to use family planning much as we had agreed to have only four children.

However, recently she conceived and when I consulted with the doctor whether my operation was was well-done, they checked and they said the operation was successful.

I'm so devastated, the doctors say it is possible the child to be mine but I'm worried.

I'm sure this child may not be mine and the mere thought of this woman having cheated on me kills me.

I have even developed hatred for all our children, I just think many or all of them are not mine.

I want to take all of them for a DNA but I'm scared. What do I do?