We shouldn’t be doing this

My friend invited me to his friend’s house for a  party, he usually never invites me, and maybe it was because he thought I really needed  to get my mind off my ex after a brutal break-up. They were not many people around, there was my friend and his girl, my friend’s friend and his girl and some 6 or so girls and boys who converged at one corner probably gossiping. 
We were playing card games in the living room, but the booze was running low, and I offered to go get some more from the back since I had no girl to be busy with except the booze. 
I was pouring the booze into the can when my friend’s friend girlfriend walked into the room and closed the door, she walked over to me and tells me that she’s been waiting to have a chance to be alone with me, claiming she was really wet and hot from fantasizing about doing it with me. It wasn’t over, I was panicking, this is the kind of situations my friends gets into being a ladies man, not me. 
She confesses that all night she has been hoping I would give her more attention, her breath is now getting heavier, and she is rubbing her hand over my trousers, I am confused but getting turned on, she takes my hand and slides it into her pants and guides it to her pussy, I feel it, I rub it, she lets out a slight moan. She moves closer, holding my shirt tightly, and tells me I was driving her crazy, and she wants to do it with me desperately. Not only that, but she kisses me, I kiss back but still wondering what is going on. She keeps  on rubbing her hand on my trouser, I am getting really hard, the kissing is getting intense, we are now breathing heavily and can’t hold anything back, she gives up slight moans as I rub her clit, she stops, unbuttons her trousers, I push her to the wall, still kissing her, and we are now dry humping with our clothes on. 
She hurriedly struggles to let loose of my trousers, but she can’t, she tells me to open it and slides her hand into my pants, finds my hard dick, it’s warm and hot, and she begins massaging it intensely. I lose my trousers, she pulls her trousers down. She holds my hands and places them on her panties that are now wet, do it, she says. 
I pull them down, and can now see her tight pussy. She holds my dick and pulls it out of my boxers, I press her harder against the wall, she is trying not to moan, but she still lets them escape her. I take my dick and slowly push it in, my dick can feel the warmth of her pussy, she starts moaning, and I have to place my hand over her mouth to control her moans. I get harder with each thrust. Her tightly pressed to the wall, I am pumping into her as hard as I can, her tight pussy getting me closer to cum with each thrust I make. Her eyes are now fully closed, her hands pressing hard into my skin, and she is biting her lips, with the occasional sounds escaping her,” oh yes, yes, fuck me, fuck me , oh yes like that, harder, oh my God, I am going to cum” and I keep on going, and then we hear footsteps approaching, we stop, go quiet and stare at each other breathing intensely. Someone calls her name. 
We remain still, and then someone suggests that she went out, the footsteps fade. ” Quick, I have to go” she says I quickly thrust into her and cum, we both hug tight as my dick shrinks and cum starts rolling down her warm thighs. She quickly wipes with a tissue and pulls her trousers up and without saying a thing she opens the door and walks out,” where were you? ” I hear someone ask her, “I was out in the back” I hear her answer. I am still shocked, happy, relieved, and exhausted. 
Quickly I  pull my trousers up and jump out of the window, fearing they might find out, and I blend into the night as I walk home.