I am getting really depressed and can't stop thinking about it. What if he is really into just one person online? What do I do?
Well, I'd be searching for the truth. And if you find another woman, I'd be confronting and saying her or me, I won't share you.
This is definitely wrong. Do not snoop. Do not confront. Do not make any ultimatums. This is completely opposite to what DBing is about. Concentrate on you. Your H is not going to tell you the truth now. He is confused and probably can't differentiate truth from fiction right now.
I disagree. You need honesty in your marriage. If he's hiding something, he's harming the marriage and keeping you from making decisions based on the truth.