So I'm being diagnosed as a borderline. 

One thing I'm not sure is normal is that I tend to black out and/or have little to no control over my actions for a period of time.

I basically switch personalities at a moment's notice from co-dependent puppy to relentlessly hostile dick. It's gotten worse to the point where friends are scared that I might actually kill them or their friends during an episode.

WTF is going on? It happens at a moments notice with or without alcohol (I don't do drugs).