Ovulation test never turned positive

Hi, so I started using ovulation predictor tests strips daily, same time every day (late morning after two hours of not drinking anything), one week before my fertile window, the week during and about 3 days after it (I have really long cycles, usually 5 1/2 weeks between). The strips never showed a positive. Is it possibly I didn't ovulate this month? I've never used the strips before and I have had one child already... Still convinced my partner to BD every other day regardless!