Seriously...do you know how babies are made? Because I don't think you know how babies are made and you shouldn't be having sex if that's the case.
She wouldn't know she's two weeks pregnant unless she was actively trying to get pregnant and taking advanced pregnancy tests only available from a doctor. Those at home pregnancy tests run much higher rates of false negatives than positives at two weeks. Which means she would have had to go to a doctor to confirm she is actually pregnant.
You need to take responsibility for your actions and make better choices. And if you can't make good decisions when you drink, you should stop drinking.
Wake up. Take her to a doctor and get her tested by a doctor or PA.
It's clear you need to learn a little more about sex, pregnancy and ways you can get STDs before engaging in sex again. You're smart enough to realize the condom is off but finish? Grow up.
While you can blame the junkie girl, so much of this situation is a result of your poor choices made when consuming alcohol. I hope you get out of this situation and learn a valuable lesson for the rest of your life because this will happen again if you don't smarten up.