Ovulation question!

Doing ovulation testing (clear blue advanced digital once a day). This is the first time I’ve done ovulation tests before. Got a negative this morning but been having EWCM this afternoon. I’m aware EWCM can come at any point in your cycle but what I’m wondering is Should I test again this evening or stick to once a day and do another in the morning? Just don’t wanna miss it. However don’t want to waste tests as they’re expensive! Cycle day 13.

Thank you