negative test, no period

Ha
So yesterday I took a clear blue pregnancy test (and the night before too, I just couldn't wait!) both came back 100% negative, no maybes about it. I searched for any line, no such luck. That was 4 days past period due (night test). And 5 days past period due (first morning urine test). I'm now on night 6 and NO spotting Yet. I had some very slight spotting yesterday but then it completely stopped. I've had some back aches, which are normal for my period, but no period?! My breasts are more sore then usual (I'm still breastfeeding my 8 month old) not sure what to do? 🤔 advice ladies? 
I was 11 days past my period do date with my first pregnancy when I tested so I had a BFP right away...