Guitar amp volume?

my amp isn't playing the music very loud at all. there is a clean/distortion switch an i HAVE to have it on distortion because you can not hear the guitar worth crap on clean. wth distortion, i have to turn it up to about 5-10 on the volume to hear it pretty good. my cousin and friend have used the amp and it plays real loud for them. i have 2 humbucker pickups, and they have 3 single coils. i dont know if this could have anything with it, but when i plug my guitar cable into my amplifier, the cable is really snug and doest move around. when it plugs into my guitar, it isnt snug, it slides right in, and you can kind of wiggle it around, which creates alot of crackle through amp. i did try to tighten the jack by taking it out, but that didn't do anything. and ofcoarse, there is the hum noise. it is not as bad as it was before i tightened it. it actually healped quite abit. please help. i dont know wether to take it to my local guitar shop or not.