Breastmilk alcohol content is the same as blood alcohol content (this isn't the same for all drugs but it is true for alcohol)
This page has a table of levels of blood alcohol content relating to level of drunkeness, obviously it's a rough guide, but you can see how low the levels really are. You'd have to be pretty drunk for your milk to even be 1% alcoholic - and bear in mind a weak alcoholic drink is about 3%. So depending on how little your LO is and how much they rely on breastmilk as their sole source of nutrition you can judge.
Added to this alcohol is processed roughly at the rate of one unit per hour so if you've drunk 5 units it will be totally out of your system 5 hours after the last drink.
As an aside there's no need to pump and dump, you can of course pump for comfort/to stimulate supply if you're away from your baby but the milk doesn't stay alcoholic in your breasts if that makes sense.
I agree with FadBook never ever drink and co-sleep, though.
Ditto the others - you didn't need to pump and dump!
My general rule of thumb is that if you can't look after yourself, you can't nurse your baby.
I can genuinely have a 4 glasses of wine and I would still feed DD. I wouldn't however, co-sleep with her after even 1 glass of wine as the whole drinking / co-sleeping worries me and I wouldn't want to risk anything happening.