How to tell if you are on your period or are having a very very early miscariage?

My period has been very strange...I am usually 26, 27 or 28 day cycle but am never less, and this month my period came on the 20th day which was strange, and then I had the strangest period because never before have I not had any cramps on my period, I am usually in bed on day one becasuse they are so bad and this period was completely painless...It was not particularly heavy it was actually a bit lighter than usual, but I am now on the 8th day of my period when never before have I had it last longer than 5 days....day 4 until now (day 8) have been extremely extremely light, only spotting, but it is the weirdest thing!

It had not even OCURRED to me until today when I was pondering this strange period ( you usually don't stop to think about being pregnant when on your period) but it ocurred to me that maybe I am having a very very early on miscariage! Unlikely because I have only had sex 3 times this cycle and all with a condom, but could this be possible?

Does anybody know any differenciating characteristics between "normal" menstural blood and miscariage blood? Or if you even bleed due to a miscariage that early on? In this case it would be between 10 and 15 days of pregnancy