Ok, for some reason, I dunno if its the shape of my fingers or what, but I absolutely cannot play a proper Bm barre chord. My index finger mutes the high E string every time and not matter what, I cannot fix it. Does anyone else have this problem with that chord, or any other chord, and can give me some good advice?

Also, I have a real problem switching between regular chords into a barre chord. I just cant make the switch smooth. For example, switching from an Em regular chord to the Bm cleanly, is for me, impossible. Is there any tricks, or mental shortcuts to make this easier?

everyone has trouble learning to switch between certain chords or forming barre chords, it's normal so just practice your way through it.
practice. practice. practice.

maybe your hands/fingers arent strong enough yet
to be more specific...

changing chords properly, fast, not only requires practice, but you should try to be aware of the tension in your fretting hand. The more tension in that hand, the harder it will be to switch chords properly
mydadisjewish = avatar stealer
I used to finger it with the barre with my first finger, then using middle, ring and pinky to finger the 3rd fret, for Bb majro. After a while i found that using ring finger as a second barre workd. just practise, like the guys sed