breastfeeding and concerned

I gave birth on Sep.25, 2016
And like it is I had my period for the whole 40 days exactly and since than I haven't had a period is that even normal??? I asked a friend and she said that it was because I was breastfeeding!!! Can that really be it? 
I have spotted on Nov. 10, 11 & 12, but no regular period so far... I've also taken pregnancy test and they've all been negative so I don't know what it is... Is any body going through the same thing?