Panties with excretions are very common in my house...even if I did not have sex (I tend to naturally lubricate)...so I don't think this is a good indicator.

Try...online monitoring system (if she uses email), monitoring pohone bills, and ASKING her.

If you're wondering, chances are that you two need to work on your marriage, regardless of whether she is cheating. Perhaps counseling is in order.

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Life is too short not to love and be loved....preferably multiple times in one night.

I think men talk to women so they can sleep with them and women sleep with men so they can talk to them. ~ Jay McInerney