Negative tests? Feeling confused 😔

Ra
Hi ladies! I'm feeling really nervous about this... I'm fairly certain I'm pregnant. I'm 3 days late (which NEVER happens), have very sore nipples, mild cramping every day for the last week and a half. I've always been very regular, and pay good attention to everything that goes on in my body, and hubby and I have been trying for 6 months now. I'm at the very least 15DPO (fertile window from December 17-22), but the tests keep coming back negative. Can anyone relate to this? I'd love some advice because I'll be a FTM and would be so thrilled to be pregnant, but am feeling really confused. Help please ladies! ❤️