Hi scale, what color is your Sport SX and the component group? odds are it is an english BB. I would overhaul it rather than keep tightening it. they call them 'fixed' cups for a reason and just tightening it with an adjustable wrench does not provide nearly enough torque. if you don't have a crank puller or BB tools already I susgest just take it to the shop. that ways if the BB is bad and you replace it with a cartridge you don't have to buy tools you may never use again.
OH is it Celeste with Sport LX shimano?
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk