So my B string is srsly fudged up.

whenever I tune it, I Can never "lock in" on the correct note. It didn't make sense since I have a decent ear. Until I picked up a tuner and hit the string. The dial which indicates the frequency would bobble back and forth OVER A WIDE RANGE. Not just a little variation. It is like my B string plays two different notes simultaneously; hence my tuner gets "confused" and cannot decide the correct frequency. I changed this string and still have the same issue.
use harmonics (touch lightly on the twelfth fret and pluck, you'll get a nice ringing sound)

The string is made up of a load of different harmonics, so if you single one out you sould get a clear note for your tuner.
sometimes my B will ring as E until it is tuned. Just find another way like 12th fret or tune like this,

5th frlow E=openA
5th fret A=openD
Don't use the tuner? Play the 4th fret on the G, and it should match the open B string, just tune it until they are the same.
The string can ring on the other side of your finger/the nut too. In many high-gain setups people stick foam behind the nut to deaden the strings from vibrating. Also if you have a tremolo certain springs will resonate at a specific frequency that could throw off your tuner. To correct this you can wrap a bubber band around the springs or stuff the cavity with tissue

When your fretting hand is closer to the nut, the strings don't touch anything from your hand to the nut. If there's a vibration strong enough the string can ring here. This is the sound you hear acoustically whenever you hammer on fairly heavy
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[thread="1166208"]Gibsons Historic Designs[/thread]
This happens with my B string aswell for some reason

Try selecting your neck pickup, roll your tone knob all the way down to zero and tune it then. Usually works for me.