jd585,
It sounds to me like your greatest concerns at this point focus around the financial. If you stick around here long enough you will read all sorts of horror stories of non-drinking spouses whose financial lives, among other things, are devastated by the other person's behavior. So no, I do not think you are making a mountain out of a molehill. If it were me, I would spend less time right now trying to figure out what my spouse is doing behind my back, and more time working to secure my finances from any further damage. From reading your posts it seems to me you may want to focus most of your energies now on protecting yourself and your family from future financial losses. IMO, the best predictor of future behavior is past behavior.
I know that many people, when they marry, join their financial lives too. I personally have never given over my money, my credit, or my financial decisions to anyone else. It sounds to me like you have given your spouse carte blanche with the income you make. If it were me, I would remove her authority and create a household budget. I would cancel all the credit cards that have my name on them, and take over paying the household bills. I would create a separate banking account for my paychecks, without anyone else's name on it. I would also insist that my spouse get a job. These actions likely will cause her to react negatively.
Please be aware that what you find out from your reconnaissance missions may be upsetting. Better to have your finances in order and your emotional life strong before the $hit hits the fan, if you get my meaning.