Tone question

-----When I played my J-bass at rehearsal, I got feedback until I
rolled off the treble on the amp.Now the bass sounds warm and fat, but
when I went to pop, I couldn't hear the note through the mix.The neck
pick-up is real hot, you can hear even a slight tap as if it were a
microphone.I've been playin a 5-string with active PU's, and haven't
had this problem.I really like the four string though, and would like
to play it more . Any ideas?