Breastfeeding and negative tests

Can breastfeeding give negative test results? Or results with extremely faint lines? I’m a week late and had sex the day before ovulation and was wondering if it could have anything to do with it because I’m getting negative tests with possibly a vvvvfl 😩 I also know that breastfeeding can cause late periods but I have never been late unless I’m pregnant. just want to know if I’m pregnant or not because I feel I am but the tests aren’t agreeing.