Am I a Plan B?

My boyfriend and I are in our late 30's and have what I thought was a happy and secure relationship. We moved in together about 9 months ago, and I take care of paying our bills and our finances. We recently changed internet service providers, and when I got the first bill I went online to register the account to pay the bill. The provider said the account number had already been registered. I asked him for the log in info, and he couldn't remember it, so I did the "forgot log in" thing, and the security question was "where did you and your spouse first meet?". I answered it, and the site said it was wrong, so I asked him. Without missing a beat, he said "OU" which is where he and his ex wife met. They have been divorced 6-7 years, and he has even been married briefly, to another woman since they divorced. I am really hurt by this. Am I unreasonable for these negative feelings???

I would say that if the security question is your only basis for your "negative feelings," then yes, you are being unreasonable. Based on your story though, your doubts regarding your husband may actually stem from a much deeper reason from even before the security question brought things to the light. Therefore, I think you have some trust issues that you need to sort out together with your husband. I would say you need to go for professional counseling (even on your own) to help you get over these issues. However, if you still feel that your suspicions are highly-justified, then you might want to try psychoanalysis on your husband: http://www.relationshippsychology.com/cheating/is-he-cheating