My suzuki gs500 want crank up?

I was ridin my suzuki GS500, bout 45min later it cut off while driving. Cranked rite back up, then started back firing,gave it more gas it started holding back and backfiring again. Then just died down. Wouldnt crank back up again. My wife had to bring my trailer to pick it up. Got home took the battery out put it on slow charger. Next day it cranked up, but running real sluggish. Change plugs, but wouldnt crank up any more. Its a 2004 Suzuki GS500f. Someone PLEASE HELP!!!