The question for you Fallen,

Do you want a clean conscience... or do you want to have a happy marriage?

If you want a happy marriage, and your wife doesn't know about your activities, then stop the activity and go about being the best husband you can be and don't tell her about it.  Don't dump the hurt on her just because you are feeling guilty.  Instead just BE a husband that does NOT do these things.

If you think that your wife has suspicions or she already knows about your activities, then stop the activity immediately, then go about being the best husband you can be and don't tell her just yet.  Start being more accountable to your wife... letting her know where you are and who you're with at all times.  Then after you have stopped the inappropriate behavior for a long period of time, then confess if you feel you must.  Let her know that you stopped the behaviors, and you have already given her more access to your whereabouts, etc.

Be prepared to accept the possibility of your wife leaving you.  But if you have already changed your behavior, and became your  best self possible, that will minimize the likelihood... 

Everybody has some degree of addictive personality... so don't let that be an excuse.  Tell your wife, you were selfish, pure and simple.

I don't necessarily think you need therapy... but that you should read some books on marriage and boundaries.

Hope this helps...
David