Regretting semi-orgy at coworker's house last night

Throw away account obviously.

So I am a 22 year-old female and started a new job at an events org about two months ago, and am getting along quite well with all of my coworkers and colleagues. It is the type of group that both works and parties together.

Yesterday, my coworker threw a memorial day BBQ and was hosting it with my boss, and invited me to come. I was having a great time and everything was going fine, and then her roommate got pretty drunk and started making out with all of the women at the BBQ (except my coworker), including me (I'm bi). It gets later, my boss leaves, but all the girls are still there.

Things started getting a little more heated, and I decide I should probably leave before anything gets out of hand. I go into one of the bedrooms to say bye, and one of the women pins me against the bed and pretty much just starts going at it with me.

The whole thing breaks out into a full on half-orgy outside on the porch between four women and one guy. Mind you, my coworker is in bed with her boyfriend, either asleep or fucking or who knows what. She comes out and sees me half naked, on some chick's lap, making out with her.

Everything stops, we clean up, and we all leave. My coworker said it was fine, but I don't know what to think. At the time, it all seemed like good fun, but now I am completely freaking out. Where do I go from here? Do I apologize to her? Act completely cool about it and just laugh it off if she brings it up?

I am afraid of this getting back to my boss and him thinking I am crazy. I usually don't do anything like this.

tl:dr Had a semi-orgy at coworker's memorial day BBQ, now scared shitless

Update: Boss found out, and talked to me about it yesterday. He thinks I started the whole thing. I think everything is fine though? Only time will tell. Time to put on my workaholic pants and keep my head down.