Please help me with my code.
here is my pinesctypt code

//@version=4
//——————————————————————————————-

  study(title="previous Week high & low", shorttitle="Prev Wk H-L", overlay=true, precision=8)
  
  prevwkH = input(true, title="Show previous week high?")
  prevwkL = input(true, title="show previous week low?")
  
  //previous week
  prevWeekHigh = security(syminfo.tickerid, '3W', high[1], lookahead=true)
  prevWeekLow = security(syminfo.tickerid, '3W', low[1], lookahead=true)
  var float weekClose = security(syminfo.tickerid, '3W', close[1])
  
  mid = (prevWeekHigh + prevWeekLow + weekClose) / 3
  upper = mid + ((prevWeekHigh - prevWeekLow) / 2)
  lower = mid - ((prevWeekHigh - prevWeekLow) / 2)
  
  //previous Week Plots
  plot(prevwkH ? mid : na, title="mid", style=plot.style_linebr, linewidth=1, color=color.fuchsia, transp=20)
  plot(prevwkL ? upper : na, title="upper", style=plot.style_linebr, linewidth=1, color=color.fuchsia, transp=20)
  plot(prevwkL ? lower : na, title="lower", style=plot.style_linebr, linewidth=1, color=color.fuchsia, transp=20)``

I want there to be plotted 3 lines for each week, but i feel like some value is not getting reset, and after a few weeks my lines are getting shifted, can somebody help me fix this?
Beginning
End

i want lines to be precise and recalculated for each week using 3 previous weeks, but they are getting shifted as if old values are used