Fatigue?

So for the past couple of days I’ve been super tired lately. Like once I get home it like I can’t even keep my eyes open. Either I’m tired from working a lot but I’ve been off from work for 3-4 days. So I sleep at night. But my period is 20 days late! I take bc pills. I take them on time for the most part. Maybe at least 30 min to an hour late sometimes at the most. I took one pregnancy test last week and it came back negative. Idk what’s going on with my body and I’m having some cramps here and there.?