Hi, I'd like to help you with your question.
If you feel your wife is not doing anything untrustworthy, then the issue originates with you. In some way, you have learned either not to trust, or you have developed a low self esteem and feel you are not worthy and your wife will want someone better.
You can easily address this issue by addressing whatever caused it in the first place. Did you experience a bad relationship in the past where you could not trust your partner? Was there abuse in your childhood or issues with trusting your parents? Do you feel you are not worth the attention and love of others? Whatever the cause, search it out and explore it. It is important to assign these feelings to where they belong, and not to your marriage or your wife.
Here are some ways you can start working on your trust issues:
One, communicate. Does your wife know how you feel? If so, she can reassure you. Talk to her about your feelings and let her know you are working on them, but in the meanwhile you are asking her to help you get this under control.
Two, work on trust in your marriage. If your wife is trustworthy in other areas of your marriage, then she can be trusted with staying faithful. But don't be afraid to tell you are afraid. Work on ways you both can trust each other. Be truthful to each other- no white lies either. Be reliable with each other. For example, if you say you are going to be somewhere at a certain time, be there. She needs to do the same. Also, put some limits on how you express feeling insecure. Don't accuse your wife of cheating and don't put undue restrictions on her to accomodate your feelings. Let her be herself, but share yourself with her.
Three, learn to trust yourself. You know yourself best and you know when you are being jealous and insecure. Work on remembering that you chose your wife and you felt she was trustworthy enough to marry her. You also have a child together which is a bond that only you two share. Remember these things when you feel insecure.
If you feel that you cannot get a handle on your feelings and it is starting to interfere in your relationship, seek out a therapist. You can talk with your doctor for a referral, or if you attend church, your pastor can help. You can also search on line at http://therapists.psychologytoday.com/rms/.
Here are some books to help you get started:
The Courage To Trust: A Guide To Building Deep And Lasting Relationships by Cynthia L. Wall and Sue Patton Thoele
Get Out of Your Own Way: Overcoming Self-Defeating Behavior by Mark Goulston and Philip Goldberg
If This Is Love Why Do I Feel So Insecure? by Carl G Hindy, J. Conrad Schwarz and Archie Brodsky
You can find these on Amazon.com or your local library may have them available.
I hope this has helped you,