hi there am hoping some people might be able to give me some practical tips in finally sdorting out my run up

i ama left arm swing bowler and each year i am constantly changing my run up at the start of the season i start by walking 20 steps ( not paces) from the front line of the batting crease and find that at the beginning this is very effective but after a while i struggle for rhythm and after several matches i reduce it to about 16 steps and again start of well but then the rhythm goes again

is there anything that will help me sort this proble out