hey guys.. need some input on my matter

iv been running test prop for the past 10weeks now .. put on some good solid gains (10kg's) but i started to plato on week 8/9/10 .. iv come across some sustanon which i was thinking to use for another 5weeks at 2ml a week bringing my whole cycle up to around the 15week mark.. would it be worth doing the sus for 5weeks? or should i be satisfied on my gains and just go onto my PCT? .. reason im worried is will i even gain on those 5weeks? or has my body seem to plato and would it be a waste? should i be better off keeping the sus for another time..

thanks in advanced

cheers