I made a huge mistake

hey there everyone please help me!!!!!!!!!!!!!!!!!!11

im 23 and my girlfriend is 20 we have been together for over a year and a half now, the other day i went out clubbing with a group of friends and ended up back at some guys house for the night.. my girlfriend hadnt come out but being absolutely paraletic id kinda forgotten that so i was lying on the floor of some guys room and this girl came up behind me and started kissing and touching me,it was rele dark so i couldnt see and i was so drunk i geunuinely thort it was my girlfriend and let her carry on. she started playing with my ... but not for long enough to make me come, (it takes me ages) we didnt kiss alot and i didnt do anything back to her and it wasnt until i woke in the morning that i realised that it hadnt been my girlfriend, i did know her but there was nothing between us and im not in the least attracted to her, it was a huge drunken mistake but now im really scared to tell her about it, shes had a past run of boyfriends who have continually cheated on her and has zero percent tollerance. i love her enormously and couldnt live without her. after i realised it hadnt been her before i threw up loads from the thought of it and have felt like crying a number of times today.it meant nothing and i am so ashamed and upset, the girl has promised never to mention it but im scared she will and i dont want to tell my grilfriend for fear of losing her. i know it sounds selfish but we love each other and both hate hate hate people who cheat, what should i do? i'd rather die than lose her shes the most brilliant thing thats ever happened to me but i know she will end it if i tell....

help me please please please

ps, i know i count it as chaeting but seeing as i techniqually didnt do anything apart from lie there and let it happen is it still real cheating? i didnt kiss her back and we didnt speak throughout i was too tired and drunk and she didnt touch herself or ask me to do so....

A mistake

hey you made a mistake,the sinning is causing pain,I suggest you just forget it,don't tell your girlfriend as it will maybe make you feel better ,but certainly not her,and i'm sure it won't happen again,if you don't know what you are doing when drunk,don't drink to that degree.Ps Yes it is cheating,whichever way you look at it. Life is a learning curve,you have learnt a hard lesson,hopefully