Bethany,
Absolutely. Some hpt's can detect hcg at low levels and this can give us a positive earlier than our period is due but sometimes ovulation could be miscalculated or sometimes there is not enough hcg in the urine to detect.
I have seen many women who got a neg and thought that was it and later found they were in fact pregnant.
I hope you get your bfp Bethany very soon...
Love and baby blessings,
DEb