I'm so embarrassed about accidentally walking in on my roommate's girlfriend in the bathroom twice
How did walking in on your roommate's girl in the bathroom happen more than once?
I was drunk and accidentally walked in and then I forgot about it and did it again a few minutes later.
You should get in the habit of always knocking before you open the bathroom door. Being drunk is no excuse for your lack of manners.
Well they should lock the door if they don't want to be seen.
You're right they should lock the door, but that doesn't take any of the blame off of you for not knocking. A simple knock at the door can really help you avoid these embarrassing situations in the future.