Help!

I gave birth Dec. 2017. my bleeding ends Jan. 15. January 20 i had my first period and it is heavy. Jan. 27, we had unprotected sex. Feb 2, i get a bleeding again. but just moderate. i just used panty liners but the red blood sometimes transfer to my underwear. (pls imagine wearing pantyliner and the blood reflects on your underwear. do you get me?) Is it normal??? another is I am expecting my next period by Feb 20 since my first is Jan. 20. I haven't got my period yet. Is it consider missed or late period even though i bleed moderately last feb 2? or could i be pregnant? please help.