Ovulation after a miscarriage


I had a miscarriage in December and since then my periods have been irregular (5 wks 4 days, 6 wks 4 days and 6 wks). I decided to start using ovulation kits this month and got the digital clear blue one. Today is cycle day 19 and still nothing. Should i be worried if the line isn’t getting any darker? I have been doing them for about a week.