never been late before

hello my partner and i been together for 3 years and now engaged we agreed to start our own family, started to ttc since last month. My cycles are between 28 days to 31 day ive done 3 pregnancy tests came bfn and now im 4 days past af was due.

Ive been having sore boobs, lower mild back pain, mild cramping on my left, felling tired during the day.

This is all new to me as i never missed a af.