i have a marshall stack and whenever im jamming with my band the feedback is so loud every time i stop playing that its almost deafening, now i have tried everything from standing as far a way as possible but still nothing and even turning it down but then i cant hear my guitar over the drums.
It is the first big amp i have ever owned so i really need some help or my band members are gonna go deaf and probly kill me.

Well try to get use to it, or when you don't play turn off the volume on the guitar.
Ibanez -> Peavey -> Eardrums

Apparently I'm on some list of people to listen to..?
too much distortion?
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Are u using single coils ? If u got too much gain + sc pups = death
well if your not playing you could turn it off or if its not playing for a few bars you could control the feedback by whammying which always souds cool

also maybe your amp has a noise reduction thing and your is off
Chuck Norris has two speeds, walk and kill
try rolling off the tone on your guitar( I'm guessing that its on 10 right now)and if you have a hollowbody try stuffing rags in the f holes