Shame on you. You made vows to love honor and obey and you broke those promises. Karmas a bitch and it's coming for you my friend.
To my knowledge, open marriages exist in this day and age... however, this particular case seems to be more oriented towards going behind the partners (in this case, his wife's) back and basically 'violating trust'.
As for Karma... numerous individuals throughout history did many highly questionable things without a consequence to their actions - it mainly depends on the people you know, how the specific information travels, who it reaches, at what time frame, and whether the receivers of information will actually decide to act on it (and then of course, there's HOW they decide to act on it).
If you want to explain this situation to your wife, that depends on several factors:
Did your wife actually see your boyfriend and knew he was there?
If yes, I suppose you could tell her that you invited him for some socializing and that you were afraid she would get mad for bringing someone so late to the house nearly half drunk (which is why you didn't tell her)... and as for the jocks being around your ankles... well, you could try saying you noticed your jocks were not exactly 'fresh' and wanted to change them, but as you noticed this, she was coming down, and you basically shoved your friend out the back door with no time for a change due to the 'panic' factor of suffering 'wife-rage'.
Its a bit of a twist on an existing situation but it DOES omit the sexual part and explains things to a degree.
Ultimately, you should be careful.
Pursuing this relationship (whatever it is) with your guy while married to a woman could end up problematic.
You could try breaching the subject with your wife to see if she'd be open to experiment with others in a purely sexual manner (opening the marriage).
At least approach it from a theoretical point of view... and if there's a chance she says 'yes' (or that she could consider it), you wouldn't have to worry so much about being caught or as if you are doing something wrong in the first place after you officially 'open' it up.
The reality is... many people go behind their partners backs (males and females alike - married or otherwise) which creates communication issues and relationships have a tendency to fall apart (although if there are no emotions anymore to back up a marriage or a relationship from either party... then, is there any purpose to maintaining it?).
If you want to preserve your marriage... you could twist the truth a little to coincide with what your wife saw (eliminating the sexual factor) therefore possibly mitigating damage from creating a perception that you were cheating on her (with a guy no less).
You could also say that you were half-drunk, horny, and relatively open to suggestion (which wouldn't be a lie because alcohol does that to people), which spiraled the situation out of control resulting in your friend orally pleasuring you.
Or since you were half-drunk, you guys were horsing around in a non-sexual way (like friends) due to intoxication and somehow ended up with your jocks around your ankles, and that you managed to get him out of the house as you heard her coming down.
you.
